{"id":"GHSA-g3qj-j598-cxmq","aliases":[],"status":"published","title":"fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing","description":"### Summary\nfido2-lib v3.x depends on cbor-x (~1.6.0), which optionally pulls in cbor-extract (C++ native addon). cbor-extract \u003c= 2.2.0 has a heap buffer over-read in `extractStrings()` — a 5-byte CBOR payload crashes Node.js with SIGSEGV. No JS exception, no try/catch, process dead.\n\nThe crash triggers during WebAuthn registration when the server decodes the attestation object. An attacker sends a crafted authenticator response to the registration endpoint — single request, unauthenticated, instant kill.\n\nFixed in cbor-extract@2.2.1 / cbor-x@1.6.3 (2026-03-08). fido2-lib@3.5.7 still pins cbor-x ~1.6.0 which resolves to vulnerable cbor-extract.\n\n## Affected versions\n\nfido2-lib \u003c= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old `cbor` package — not affected.\n\nOnly affects systems where `cbor-extract` native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe.\n\n## PoC\n\n```js\nconst { decode } = require(\"cbor-x\");\ndecode(Buffer.from(\"7a10000000\", \"hex\")); // exit code 139 (SIGSEGV)\n```\n\nCBOR text string header claiming 268MB in a 5-byte buffer. `extractStrings()` in extract.cpp line 87 calls `readString()` without bounds check. Reads past buffer into unmapped memory.\n\nIn context: attacker intercepts WebAuthn registration response, replaces `attestationObject` with the 5-byte payload, POSTs to the registration verification endpoint. Server calls `attestationResult()` → `cbor-x.decode()` → `cbor-extract` → SIGSEGV.\n\n## Fix\n\nBump cbor-x to \u003e= 1.6.3 (which pulls cbor-extract \u003e= 2.2.1).\n\n```diff\n-\"cbor-x\": \"~1.6.0\"\n+\"cbor-x\": \"^1.6.3\"\n```\n\n— Malik X (@Xvush)","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","from":"ghsa"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-125","CWE-126","CWE-1395"],"published":"2026-03-24T19:10:38Z","modified":"2026-03-24T19:16:32Z","fixes":[{"ecosystem":"npm","package":"fido2-lib","fixed_in":["3.5.8"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"fido2-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"3.5.7"},{"fixed":"3.5.8"}]}]},{"source":"osv","ecosystem":"npm","package":"fido2-lib","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.5.8"}]}]}],"references":[{"url":"https://github.com/webauthn-open-source/fido2-lib/security/advisories/GHSA-g3qj-j598-cxmq","tags":["web"]},{"url":"https://github.com/kriszyp/cbor-extract/issues/2","tags":["web"]},{"url":"https://github.com/kriszyp/cbor-extract/issues/3","tags":["web"]},{"url":"https://github.com/kriszyp/cbor-extract/commit/1f6e0d9704149bdb5531d25f5d08a0280a71e2ca","tags":["web"]},{"url":"https://github.com/advisories/GHSA-g3qj-j598-cxmq"},{"url":"https://github.com/webauthn-open-source/fido2-lib","tags":["package"]}],"sources":{"ghsa":[{"id":"GHSA-g3qj-j598-cxmq","title":"fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing","description":"### Summary\nfido2-lib v3.x depends on cbor-x (~1.6.0), which optionally pulls in cbor-extract (C++ native addon). cbor-extract \u003c= 2.2.0 has a heap buffer over-read in `extractStrings()` — a 5-byte CBOR payload crashes Node.js with SIGSEGV. No JS exception, no try/catch, process dead.\n\nThe crash triggers during WebAuthn registration when the server decodes the attestation object. An attacker sends a crafted authenticator response to the registration endpoint — single request, unauthenticated, instant kill.\n\nFixed in cbor-extract@2.2.1 / cbor-x@1.6.3 (2026-03-08). fido2-lib@3.5.7 still pins cbor-x ~1.6.0 which resolves to vulnerable cbor-extract.\n\n## Affected versions\n\nfido2-lib \u003c= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old `cbor` package — not affected.\n\nOnly affects systems where `cbor-extract` native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe.\n\n## PoC\n\n```js\nconst { decode } = require(\"cbor-x\");\ndecode(Buffer.from(\"7a10000000\", \"hex\")); // exit code 139 (SIGSEGV)\n```\n\nCBOR text string header claiming 268MB in a 5-byte buffer. `extractStrings()` in extract.cpp line 87 calls `readString()` without bounds check. Reads past buffer into unmapped memory.\n\nIn context: attacker intercepts WebAuthn registration response, replaces `attestationObject` with the 5-byte payload, POSTs to the registration verification endpoint. Server calls `attestationResult()` → `cbor-x.decode()` → `cbor-extract` → SIGSEGV.\n\n## Fix\n\nBump cbor-x to \u003e= 1.6.3 (which pulls cbor-extract \u003e= 2.2.1).\n\n```diff\n-\"cbor-x\": \"~1.6.0\"\n+\"cbor-x\": \"^1.6.3\"\n```\n\n— Malik X (@Xvush)","status":"published","published":"2026-03-24T19:10:38Z","modified":"2026-03-24T19:10:41Z","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-125","CWE-126","CWE-1395"],"updated_at":"2026-11-02T14:39:41.724707Z"}],"osv":[{"id":"GHSA-g3qj-j598-cxmq","title":"fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing","description":"### Summary\nfido2-lib v3.x depends on cbor-x (~1.6.0), which optionally pulls in cbor-extract (C++ native addon). cbor-extract \u003c= 2.2.0 has a heap buffer over-read in `extractStrings()` — a 5-byte CBOR payload crashes Node.js with SIGSEGV. No JS exception, no try/catch, process dead.\n\nThe crash triggers during WebAuthn registration when the server decodes the attestation object. An attacker sends a crafted authenticator response to the registration endpoint — single request, unauthenticated, instant kill.\n\nFixed in cbor-extract@2.2.1 / cbor-x@1.6.3 (2026-03-08). fido2-lib@3.5.7 still pins cbor-x ~1.6.0 which resolves to vulnerable cbor-extract.\n\n## Affected versions\n\nfido2-lib \u003c= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old `cbor` package — not affected.\n\nOnly affects systems where `cbor-extract` native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe.\n\n## PoC\n\n```js\nconst { decode } = require(\"cbor-x\");\ndecode(Buffer.from(\"7a10000000\", \"hex\")); // exit code 139 (SIGSEGV)\n```\n\nCBOR text string header claiming 268MB in a 5-byte buffer. `extractStrings()` in extract.cpp line 87 calls `readString()` without bounds check. Reads past buffer into unmapped memory.\n\nIn context: attacker intercepts WebAuthn registration response, replaces `attestationObject` with the 5-byte payload, POSTs to the registration verification endpoint. Server calls `attestationResult()` → `cbor-x.decode()` → `cbor-extract` → SIGSEGV.\n\n## Fix\n\nBump cbor-x to \u003e= 1.6.3 (which pulls cbor-extract \u003e= 2.2.1).\n\n```diff\n-\"cbor-x\": \"~1.6.0\"\n+\"cbor-x\": \"^1.6.3\"\n```\n\n— Malik X (@Xvush)","status":"published","published":"2026-03-24T19:10:38Z","modified":"2026-03-24T19:16:32.00003Z","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-125","CWE-126","CWE-1395"],"updated_at":"2026-11-02T15:46:47.119724Z"}]}}