{"id":"CVE-2026-46673","aliases":["DEBIAN-CVE-2026-46673","EUVD-2026-36124","GHSA-g9f8-wqj9-fjw5","RUSTSEC-2026-0153","RUSTSEC-2026-0154"],"status":"published","title":"Russh: Unchecked CryptoVec allocation and growth handling is reachable from local agent inputs in current russh releases and from remote SSH traffic in historical pre-0.58.0 releases","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00263,"percentile":0.18175,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-770"],"published":"2026-05-15T12:00:00Z","modified":"2026-10-28T02:31:12Z","fixes":[{"ecosystem":"crates.io","package":"russh-cryptovec","fixed_in":["0.60.3"],"sources":["ghsa","osv"]},{"ecosystem":"crates.io","package":"russh","fixed_in":["0.60.3"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"rust-russh","fixed_in":["0.64.1-1"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"rust-russh-cryptovec","fixed_in":["0.62.0-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"russh-cryptovec","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.60.2"},{"fixed":"0.60.3"}]}]},{"source":"ghsa","ecosystem":"crates.io","package":"russh","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.60.2"},{"fixed":"0.60.3"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"rust-russh","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.64.1-1"}]}],"versions":["0.57.1-1","0.57.1-2"]},{"source":"osv","ecosystem":"Debian:14","package":"rust-russh-cryptovec","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.62.0-1"}]}],"versions":["0.52.0-1","0.58.0-1","0.59.0-1"]},{"source":"osv","ecosystem":"crates.io","package":"russh-cryptovec","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.60.3"}]}]},{"source":"osv","ecosystem":"crates.io","package":"russh","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.60.3"}]}]},{"source":"osv","ecosystem":"crates.io","package":"russh-cryptovec","ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"0.60.3"}]}]},{"source":"osv","ecosystem":"crates.io","package":"russh","ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"0.60.3"}]}]}],"products":[{"vendor":"eugeny","product":"russh"}],"references":[{"url":"https://github.com/Eugeny/russh/security/advisories/GHSA-g9f8-wqj9-fjw5","tags":["x_refsource_CONFIRM","exploit","advisory","web"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0153.html","tags":["web","advisory"]},{"url":"https://rustsec.org/advisories/RUSTSEC-2026-0154.html","tags":["web","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-46673","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-g9f8-wqj9-fjw5"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/46xxx/CVE-2026-46673.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-46673","tags":["advisory"]},{"url":"https://github.com/Eugeny/russh","tags":["package"]},{"url":"https://crates.io/crates/russh-cryptovec","tags":["package"]},{"url":"https://github.com/Eugeny/russh/commit/a2d48a71fe93d18cbd666c8d53d0882f5ce110c4","tags":["web"]},{"url":"https://crates.io/crates/russh","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-46673","title":"Russh: Unchecked CryptoVec allocation and growth handling is reachable from local agent inputs in current russh releases and from remote SSH traffic in historical pre-0.58.0 releases","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","status":"published","published":"2026-06-10T20:16:28.001Z","modified":"2026-06-11T14:33:14.237Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T13:46:55.086623Z"}],"euvd":[{"id":"EUVD-2026-36124","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","status":"published","published":"2026-06-10T20:16:28Z","modified":"2026-06-11T14:33:14Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T18:20:44.061211Z"}],"ghsa":[{"id":"GHSA-g9f8-wqj9-fjw5","title":"Russh: Unchecked CryptoVec allocation and growth handling is reachable","description":"### Title\nUnchecked `CryptoVec` allocation and growth handling was reachable from local agent inputs in current `russh` releases and from remote SSH traffic in historical pre-`0.58.0` releases\n\n### Summary\n`CryptoVec` used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current `russh` releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older `russh` releases before `0.58.0`, remote SSH traffic also reached `CryptoVec` through transport and compression buffers.\n\n### Details\nThe underlying unsafe paths were in `CryptoVec`:\n\n- `cryptovec/src/cryptovec.rs`\n  - unchecked capacity growth\n  - unchecked length arithmetic in growth callers\n  - raw allocation and reallocation paths coupled to those sizes\n- `cryptovec/src/platform/unix.rs`\n  - `mlock` / `munlock` previously accepted zero-length calls and performed null-pointer validation inside the `unsafe` OS-call path\n\nThere are two relevant reachability stories:\n\n1. current local reachability in `russh`\n\n- `russh/src/keys/agent/client.rs`\n  - `AgentClient::read_response()` read a peer-supplied `u32` length and then resized `self.buf` to that value before reading the payload\n- `russh/src/keys/agent/server.rs`\n  - `Connection::run()` read a peer-supplied `u32` length and then resized `self.buf` to that value before reading the payload\n\nThis is the path that still existed in current `0.60.x` releases before the fix, although by then those buffers were no longer `CryptoVec`.\n\n2. historical remote reachability in older `russh`\n\n- before commit `712e32b` (first released in `v0.58.0`), non-secret transport and compression buffers in `russh` still used `CryptoVec`\n- I verified this in a detached pre-`712e32b` worktree by adding and running:\n  - `cipher::tests::remote_packet_length_grows_transport_cryptovec_buffer`\n  - `compression::tests::remote_compressed_payload_expands_cryptovec_output`\n- those tests show that remote SSH traffic could grow `CryptoVec` through:\n  - transport packet reads\n  - zlib decompression output\n\nAlso added a constrained-memory reproduction in that historical worktree:\n\n- `compression::tests::remote_compressed_payload_can_crash_under_memory_limit`\n\nThat test re-execs the test binary under `prlimit --as=134217728`, decompresses a highly compressible payload that expands to `96 MiB`, and reliably aborts in the old Unix `CryptoVec` path when `NonNull::new_unchecked()` receives a null pointer after allocation failure.\n\nThe prepared patch does two things:\n\n1. hardens `CryptoVec` itself\n   - checked capacity growth\n   - checked length arithmetic\n   - immediate allocation-failure handling\n   - zero-length `mlock` / `munlock` no-ops\n   - explicit null-pointer validation before entering the Unix `unsafe` locking calls\n\n2. hardens the real untrusted-input path\n   - caps agent frame lengths at `256 * 1024` on both client and server before resizing buffers\n\nThis cap matches OpenSSH’s agent framing guardrail.\n\n### PoC\nThe following end-to-end tests demonstrate the real untrusted-input path by feeding oversized peer-controlled agent frame lengths into the public client and server flows and asserting that they are rejected before buffer growth.\n\nClient-side agent reply path:\n\n```rust\n#[test]\nfn oversized_agent_response_is_rejected_before_allocation() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let (mut writer, reader) = tokio::io::duplex(64);\n        let server = tokio::spawn(async move {\n            let mut frame = [0u8; 4];\n            writer.read_exact(\u0026mut frame).await?;\n            let len = BigEndian::read_u32(\u0026frame) as usize;\n            let mut body = vec![0; len];\n            writer.read_exact(\u0026mut body).await?;\n\n            BigEndian::write_u32(\u0026mut frame, (MAX_AGENT_FRAME_LEN + 1) as u32);\n            writer.write_all(\u0026frame).await?;\n            Ok::\u003c(), std::io::Error\u003e(())\n        });\n\n        let mut client = AgentClient::connect(reader);\n        let err = client.request_identities().await.unwrap_err();\n        assert!(matches!(err, Error::AgentProtocolError));\n        server.await.expect(\"server task\")?;\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nServer-side agent request path:\n\n```rust\n#[test]\nfn oversized_agent_request_is_rejected_before_allocation() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let (server, mut client) = tokio::io::duplex(64);\n        let connection = Connection {\n            lock: Lock(std::sync::Arc::new(std::sync::RwLock::new(crate::CryptoVec::new()))),\n            keys: KeyStore(std::sync::Arc::new(std::sync::RwLock::new(\n                std::collections::HashMap::new(),\n            ))),\n            agent: Some(()),\n            s: server,\n            buf: Vec::new(),\n        };\n        let server = tokio::spawn(async move { connection.run().await });\n\n        let mut frame = [0u8; 4];\n        BigEndian::write_u32(\u0026mut frame, (MAX_AGENT_FRAME_LEN + 1) as u32);\n        client.write_all(\u0026frame).await?;\n        drop(client);\n\n        let err = server.await.expect(\"server task\").unwrap_err();\n        assert!(matches!(err, Error::AgentProtocolError));\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nThese tests pass on the fixed branch and fail on unfixed `v0.60.2`, where oversized agent frame lengths are not rejected at the framing boundary.\n\nFor historical `russh \u003c 0.58.0`, I also verified remote reachability into `CryptoVec` in a detached pre-`712e32b` worktree (`91d431d`, package version `0.57.1`).\n\nTransport packet read path:\n\n```rust\n#[test]\nfn remote_packet_length_grows_transport_cryptovec_buffer() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let packet_len = MAXIMUM_PACKET_LEN;\n        let (mut writer, mut reader) = tokio::io::duplex(packet_len + 4);\n        let writer_task = tokio::spawn(async move {\n            let mut packet = vec![0u8; packet_len + 4];\n            packet[..4].copy_from_slice(\u0026(packet_len as u32).to_be_bytes());\n            writer.write_all(\u0026packet).await?;\n            Ok::\u003c(), std::io::Error\u003e(())\n        });\n\n        let mut buffer = SSHBuffer::new();\n        let mut cipher = clear::Key;\n        let n = read(\u0026mut reader, \u0026mut buffer, \u0026mut cipher).await.unwrap();\n\n        assert_eq!(n, packet_len + 4);\n        assert_eq!(buffer.buffer.len(), packet_len + 4);\n        assert_eq!(\u0026buffer.buffer[..4], \u0026(packet_len as u32).to_be_bytes());\n\n        writer_task.await.expect(\"writer task\")?;\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nCompression growth path:\n\n```rust\n#[test]\nfn remote_compressed_payload_expands_cryptovec_output() {\n    let payload = vec![b'A'; 64 * 1024];\n\n    let compression = Compression::new(\u0026ZLIB);\n    let mut compressor = Compress::None;\n    let mut decompressor = Decompress::None;\n    compression.init_compress(\u0026mut compressor);\n    compression.init_decompress(\u0026mut decompressor);\n\n    let mut compressed = CryptoVec::new();\n    let encoded = compressor\n        .compress(\u0026payload, \u0026mut compressed)\n        .expect(\"compress\")\n        .to_vec();\n\n    let mut output = CryptoVec::new();\n    let decoded = decompressor\n        .decompress(\u0026encoded, \u0026mut output)\n        .expect(\"decompress\");\n\n    assert_eq!(decoded.len(), payload.len());\n    assert_eq!(decoded, payload.as_slice());\n    assert!(encoded.len() \u003c output.len());\n}\n```\n\nConstrained-memory crash reproduction for the historical remote compression path:\n\n```rust\n#[test]\nfn remote_compressed_payload_can_crash_under_memory_limit() {\n    const CHILD_ENV: \u0026str = \"RUSSH_REMOTE_COMPRESS_CRASH_CHILD\";\n\n    if std::env::var_os(CHILD_ENV).is_some() {\n        let payload = vec![b'A'; 96 * 1024 * 1024];\n\n        let compression = Compression::new(\u0026ZLIB);\n        let mut compressor = Compress::None;\n        let mut decompressor = Decompress::None;\n        compression.init_compress(\u0026mut compressor);\n        compression.init_decompress(\u0026mut decompressor);\n\n        let mut compressed = CryptoVec::new();\n        let encoded = compressor\n            .compress(\u0026payload, \u0026mut compressed)\n            .expect(\"compress\")\n            .to_vec();\n\n        let mut output = CryptoVec::new();\n        let decoded = decompressor\n            .decompress(\u0026encoded, \u0026mut output)\n            .expect(\"decompress\");\n        assert_eq!(decoded.len(), payload.len());\n        return;\n    }\n\n    let exe = std::env::current_exe().expect(\"current exe\");\n    let status = Command::new(\"prlimit\")\n        .args([\n            \"--as=134217728\",\n            \"--\",\n            exe.to_str().expect(\"utf8 exe path\"),\n            \"--exact\",\n            \"compression::tests::remote_compressed_payload_can_crash_under_memory_limit\",\n            \"--nocapture\",\n        ])\n        .env(CHILD_ENV, \"1\")\n        .status()\n        .expect(\"spawn child\");\n\n    assert!(\n        !status.success(),\n        \"expected child to fail under constrained address space\"\n    );\n}\n```\n\nOn that historical worktree, the constrained-memory child aborts in the old Unix `CryptoVec` path with:\n\n```text\nunsafe precondition(s) violated: NonNull::new_unchecked requires that the pointer is non-null\nthread caused non-unwinding panic. aborting.\n```\n\nTo run the reproduced checks:\n\n```bash\ncargo test -p russh oversized_agent_response_is_rejected_before_allocation -- --nocapture\ncargo test -p russh oversized_agent_request_is_rejected_before_allocation -- --nocapture\ncargo test -p russh-cryptovec\n```\n\nHistorical pre-`0.58.0` checks were run from the detached `91d431d` worktree with:\n\n```bash\ncargo test --offline -p russh remote_packet_length_grows_transport_cryptovec_buffer -- --nocapture\ncargo test --offline -p russh remote_compressed_payload_expands_cryptovec_output -- --nocapture\ncargo test --offline -p russh remote_compressed_payload_can_crash_under_memory_limit -- --nocapture\n```\n\n### Impact\nThis is a memory-safety hardening issue with demonstrated untrusted-input reachability.\n\nWhat is demonstrated:\n\n- current local agent peers could previously reach allocation growth directly from attacker-controlled frame lengths\n- historical remote SSH traffic could previously reach `CryptoVec` through transport and compression buffers in `russh \u003c 0.58.0`\n- under constrained memory, the historical remote compression path can be turned into a process abort in the old Unix `CryptoVec` code\n- the fixed code now rejects oversized agent frames early and hardens the underlying allocation paths\n\nWhat is not demonstrated:\n\n- practical code execution\n- a demonstrated integrity or confidentiality break","status":"published","published":"2026-05-21T20:49:07Z","modified":"2026-06-11T14:06:42Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:40:26.12116Z"}],"nvd":[{"id":"CVE-2026-46673","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","status":"published","published":"2026-06-10T22:17:00.167Z","modified":"2026-07-23T09:10:00.113Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T14:12:23.485267Z"}],"osv":[{"id":"CVE-2026-46673","title":"Russh: Unchecked CryptoVec allocation and growth handling is reachable from local agent inputs in current russh releases and from remote SSH traffic in historical pre-0.58.0 releases","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","status":"published","published":"2026-06-10T20:16:28.001Z","modified":"2026-10-28T02:31:12.692058066Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:45:06.231145Z"},{"id":"DEBIAN-CVE-2026-46673","description":"Russh is a Rust SSH client \u0026 server library. Prior to version 0.60.3, CryptoVec used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current russh releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older russh releases before 0.58.0, remote SSH traffic also reached CryptoVec through transport and compression buffers. This issue has been patched in version 0.60.3.","status":"published","published":"2026-06-10T22:17:00.167Z","modified":"2026-10-14T16:00:16.57018356Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:56.444225Z"},{"id":"GHSA-g9f8-wqj9-fjw5","title":"Russh: Unchecked CryptoVec allocation and growth handling is reachable","description":"### Title\nUnchecked `CryptoVec` allocation and growth handling was reachable from local agent inputs in current `russh` releases and from remote SSH traffic in historical pre-`0.58.0` releases\n\n### Summary\n`CryptoVec` used unchecked capacity growth, unchecked length arithmetic, and unsafe allocation/locking paths. In current `russh` releases, local SSH agent peers could still feed attacker-controlled frame lengths into buffer growth before validation. In older `russh` releases before `0.58.0`, remote SSH traffic also reached `CryptoVec` through transport and compression buffers.\n\n### Details\nThe underlying unsafe paths were in `CryptoVec`:\n\n- `cryptovec/src/cryptovec.rs`\n  - unchecked capacity growth\n  - unchecked length arithmetic in growth callers\n  - raw allocation and reallocation paths coupled to those sizes\n- `cryptovec/src/platform/unix.rs`\n  - `mlock` / `munlock` previously accepted zero-length calls and performed null-pointer validation inside the `unsafe` OS-call path\n\nThere are two relevant reachability stories:\n\n1. current local reachability in `russh`\n\n- `russh/src/keys/agent/client.rs`\n  - `AgentClient::read_response()` read a peer-supplied `u32` length and then resized `self.buf` to that value before reading the payload\n- `russh/src/keys/agent/server.rs`\n  - `Connection::run()` read a peer-supplied `u32` length and then resized `self.buf` to that value before reading the payload\n\nThis is the path that still existed in current `0.60.x` releases before the fix, although by then those buffers were no longer `CryptoVec`.\n\n2. historical remote reachability in older `russh`\n\n- before commit `712e32b` (first released in `v0.58.0`), non-secret transport and compression buffers in `russh` still used `CryptoVec`\n- I verified this in a detached pre-`712e32b` worktree by adding and running:\n  - `cipher::tests::remote_packet_length_grows_transport_cryptovec_buffer`\n  - `compression::tests::remote_compressed_payload_expands_cryptovec_output`\n- those tests show that remote SSH traffic could grow `CryptoVec` through:\n  - transport packet reads\n  - zlib decompression output\n\nAlso added a constrained-memory reproduction in that historical worktree:\n\n- `compression::tests::remote_compressed_payload_can_crash_under_memory_limit`\n\nThat test re-execs the test binary under `prlimit --as=134217728`, decompresses a highly compressible payload that expands to `96 MiB`, and reliably aborts in the old Unix `CryptoVec` path when `NonNull::new_unchecked()` receives a null pointer after allocation failure.\n\nThe prepared patch does two things:\n\n1. hardens `CryptoVec` itself\n   - checked capacity growth\n   - checked length arithmetic\n   - immediate allocation-failure handling\n   - zero-length `mlock` / `munlock` no-ops\n   - explicit null-pointer validation before entering the Unix `unsafe` locking calls\n\n2. hardens the real untrusted-input path\n   - caps agent frame lengths at `256 * 1024` on both client and server before resizing buffers\n\nThis cap matches OpenSSH’s agent framing guardrail.\n\n### PoC\nThe following end-to-end tests demonstrate the real untrusted-input path by feeding oversized peer-controlled agent frame lengths into the public client and server flows and asserting that they are rejected before buffer growth.\n\nClient-side agent reply path:\n\n```rust\n#[test]\nfn oversized_agent_response_is_rejected_before_allocation() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let (mut writer, reader) = tokio::io::duplex(64);\n        let server = tokio::spawn(async move {\n            let mut frame = [0u8; 4];\n            writer.read_exact(\u0026mut frame).await?;\n            let len = BigEndian::read_u32(\u0026frame) as usize;\n            let mut body = vec![0; len];\n            writer.read_exact(\u0026mut body).await?;\n\n            BigEndian::write_u32(\u0026mut frame, (MAX_AGENT_FRAME_LEN + 1) as u32);\n            writer.write_all(\u0026frame).await?;\n            Ok::\u003c(), std::io::Error\u003e(())\n        });\n\n        let mut client = AgentClient::connect(reader);\n        let err = client.request_identities().await.unwrap_err();\n        assert!(matches!(err, Error::AgentProtocolError));\n        server.await.expect(\"server task\")?;\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nServer-side agent request path:\n\n```rust\n#[test]\nfn oversized_agent_request_is_rejected_before_allocation() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let (server, mut client) = tokio::io::duplex(64);\n        let connection = Connection {\n            lock: Lock(std::sync::Arc::new(std::sync::RwLock::new(crate::CryptoVec::new()))),\n            keys: KeyStore(std::sync::Arc::new(std::sync::RwLock::new(\n                std::collections::HashMap::new(),\n            ))),\n            agent: Some(()),\n            s: server,\n            buf: Vec::new(),\n        };\n        let server = tokio::spawn(async move { connection.run().await });\n\n        let mut frame = [0u8; 4];\n        BigEndian::write_u32(\u0026mut frame, (MAX_AGENT_FRAME_LEN + 1) as u32);\n        client.write_all(\u0026frame).await?;\n        drop(client);\n\n        let err = server.await.expect(\"server task\").unwrap_err();\n        assert!(matches!(err, Error::AgentProtocolError));\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nThese tests pass on the fixed branch and fail on unfixed `v0.60.2`, where oversized agent frame lengths are not rejected at the framing boundary.\n\nFor historical `russh \u003c 0.58.0`, I also verified remote reachability into `CryptoVec` in a detached pre-`712e32b` worktree (`91d431d`, package version `0.57.1`).\n\nTransport packet read path:\n\n```rust\n#[test]\nfn remote_packet_length_grows_transport_cryptovec_buffer() -\u003e std::io::Result\u003c()\u003e {\n    let runtime = tokio::runtime::Builder::new_current_thread()\n        .enable_all()\n        .build()?;\n\n    runtime.block_on(async {\n        let packet_len = MAXIMUM_PACKET_LEN;\n        let (mut writer, mut reader) = tokio::io::duplex(packet_len + 4);\n        let writer_task = tokio::spawn(async move {\n            let mut packet = vec![0u8; packet_len + 4];\n            packet[..4].copy_from_slice(\u0026(packet_len as u32).to_be_bytes());\n            writer.write_all(\u0026packet).await?;\n            Ok::\u003c(), std::io::Error\u003e(())\n        });\n\n        let mut buffer = SSHBuffer::new();\n        let mut cipher = clear::Key;\n        let n = read(\u0026mut reader, \u0026mut buffer, \u0026mut cipher).await.unwrap();\n\n        assert_eq!(n, packet_len + 4);\n        assert_eq!(buffer.buffer.len(), packet_len + 4);\n        assert_eq!(\u0026buffer.buffer[..4], \u0026(packet_len as u32).to_be_bytes());\n\n        writer_task.await.expect(\"writer task\")?;\n        Ok::\u003c(), std::io::Error\u003e(())\n    })?;\n\n    Ok(())\n}\n```\n\nCompression growth path:\n\n```rust\n#[test]\nfn remote_compressed_payload_expands_cryptovec_output() {\n    let payload = vec![b'A'; 64 * 1024];\n\n    let compression = Compression::new(\u0026ZLIB);\n    let mut compressor = Compress::None;\n    let mut decompressor = Decompress::None;\n    compression.init_compress(\u0026mut compressor);\n    compression.init_decompress(\u0026mut decompressor);\n\n    let mut compressed = CryptoVec::new();\n    let encoded = compressor\n        .compress(\u0026payload, \u0026mut compressed)\n        .expect(\"compress\")\n        .to_vec();\n\n    let mut output = CryptoVec::new();\n    let decoded = decompressor\n        .decompress(\u0026encoded, \u0026mut output)\n        .expect(\"decompress\");\n\n    assert_eq!(decoded.len(), payload.len());\n    assert_eq!(decoded, payload.as_slice());\n    assert!(encoded.len() \u003c output.len());\n}\n```\n\nConstrained-memory crash reproduction for the historical remote compression path:\n\n```rust\n#[test]\nfn remote_compressed_payload_can_crash_under_memory_limit() {\n    const CHILD_ENV: \u0026str = \"RUSSH_REMOTE_COMPRESS_CRASH_CHILD\";\n\n    if std::env::var_os(CHILD_ENV).is_some() {\n        let payload = vec![b'A'; 96 * 1024 * 1024];\n\n        let compression = Compression::new(\u0026ZLIB);\n        let mut compressor = Compress::None;\n        let mut decompressor = Decompress::None;\n        compression.init_compress(\u0026mut compressor);\n        compression.init_decompress(\u0026mut decompressor);\n\n        let mut compressed = CryptoVec::new();\n        let encoded = compressor\n            .compress(\u0026payload, \u0026mut compressed)\n            .expect(\"compress\")\n            .to_vec();\n\n        let mut output = CryptoVec::new();\n        let decoded = decompressor\n            .decompress(\u0026encoded, \u0026mut output)\n            .expect(\"decompress\");\n        assert_eq!(decoded.len(), payload.len());\n        return;\n    }\n\n    let exe = std::env::current_exe().expect(\"current exe\");\n    let status = Command::new(\"prlimit\")\n        .args([\n            \"--as=134217728\",\n            \"--\",\n            exe.to_str().expect(\"utf8 exe path\"),\n            \"--exact\",\n            \"compression::tests::remote_compressed_payload_can_crash_under_memory_limit\",\n            \"--nocapture\",\n        ])\n        .env(CHILD_ENV, \"1\")\n        .status()\n        .expect(\"spawn child\");\n\n    assert!(\n        !status.success(),\n        \"expected child to fail under constrained address space\"\n    );\n}\n```\n\nOn that historical worktree, the constrained-memory child aborts in the old Unix `CryptoVec` path with:\n\n```text\nunsafe precondition(s) violated: NonNull::new_unchecked requires that the pointer is non-null\nthread caused non-unwinding panic. aborting.\n```\n\nTo run the reproduced checks:\n\n```bash\ncargo test -p russh oversized_agent_response_is_rejected_before_allocation -- --nocapture\ncargo test -p russh oversized_agent_request_is_rejected_before_allocation -- --nocapture\ncargo test -p russh-cryptovec\n```\n\nHistorical pre-`0.58.0` checks were run from the detached `91d431d` worktree with:\n\n```bash\ncargo test --offline -p russh remote_packet_length_grows_transport_cryptovec_buffer -- --nocapture\ncargo test --offline -p russh remote_compressed_payload_expands_cryptovec_output -- --nocapture\ncargo test --offline -p russh remote_compressed_payload_can_crash_under_memory_limit -- --nocapture\n```\n\n### Impact\nThis is a memory-safety hardening issue with demonstrated untrusted-input reachability.\n\nWhat is demonstrated:\n\n- current local agent peers could previously reach allocation growth directly from attacker-controlled frame lengths\n- historical remote SSH traffic could previously reach `CryptoVec` through transport and compression buffers in `russh \u003c 0.58.0`\n- under constrained memory, the historical remote compression path can be turned into a process abort in the old Unix `CryptoVec` code\n- the fixed code now rejects oversized agent frames early and hardens the underlying allocation paths\n\nWhat is not demonstrated:\n\n- practical code execution\n- a demonstrated integrity or confidentiality break","status":"published","published":"2026-05-21T20:49:07Z","modified":"2026-09-10T03:51:05.593041447Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-770"],"updated_at":"2026-11-02T15:46:47.472172Z"},{"id":"RUSTSEC-2026-0153","title":"Unchecked `CryptoVec` allocation and growth handling","description":"`CryptoVec` used unchecked capacity growth, unchecked length arithmetic, and\nunsafe allocation and locking paths. In affected `russh` releases,\nattacker-controlled input could reach these code paths through buffer resizing\noperations.\n\nTwo affected reachability paths were identified:\n\n* **Current `russh` releases (`0.60.x` before the fix)**\n  Local SSH agent peers could provide attacker-controlled frame lengths that\n  were used to resize internal buffers before validation in:\n\n  * `AgentClient::read_response`\n  * `agent::server::Connection::run`\n\n* **Historical `russh` releases before `0.58.0`**\n  `CryptoVec` was also used for non-secret transport and compression buffers,\n  allowing remote SSH traffic to trigger `CryptoVec` growth through:\n\n  * transport packet reads\n  * zlib decompression output\n\nThese remote paths were removed in `0.58.0` when `CryptoVec` stopped being used\nfor those buffers.\n\nUnder constrained memory conditions, historical `russh` versions prior to\n`0.58.0` can abort the process when remote compressed payload expansion causes\nallocation failure in `CryptoVec`. This was reproduced through the compression\npath and resulted in process termination in the Unix allocation/locking\nimplementation after null pointer allocation failure.\n\nFor current affected releases, oversized local SSH agent frame lengths could\ntrigger untrusted-input-driven buffer growth prior to validation.\n\nNo practical remote code execution, integrity or confidentiality impact has\nbeen demonstrated.\n\nFixed by validating CryptoVec growth operations and rejecting oversized SSH\nagent frame lengths before buffer allocation.","status":"published","published":"2026-05-15T12:00:00Z","modified":"2026-10-12T18:00:09.237854178Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:53:40.430679Z"},{"id":"RUSTSEC-2026-0154","title":"Unbounded 32-bit allocation","description":"Both the SSH agent server and client accepted peer-controlled frame lengths\nwithout enforcing a maximum frame size. This could cause large memory\nallocations while parsing a maliciously crafted agent frame.\n\nA malicious peer could advertise an oversized frame length, causing the client\nor server to attempt a large memory allocation before validating the frame,\npotentially leading to memory exhaustion or process termination.\n\nThis is fixed by enforcing a maximum agent frame size of 256 KiB and\nrejecting oversized frames before buffer allocation.","status":"published","published":"2026-05-15T12:00:00Z","modified":"2026-10-12T18:00:13.569892882Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:53:40.430679Z"}]}}