{"id":"CVE-2026-62847","aliases":["EUVD-2026-114452","GHSA-m6wq-39m7-9xpp"],"status":"published","title":"Metalama: Local code execution via DLL planting in world-writable temporary directories (Linux/macOS)","description":"Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.","severity":{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00151,"percentile":0.04303,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-377","CWE-427"],"published":"2026-10-14T19:24:53Z","modified":"2026-11-04T02:30:19Z","fixes":[{"ecosystem":"NuGet","package":"Metalama.Framework","fixed_in":["2026.1.19","2025.1.18","2026.0.25"],"sources":["ghsa","osv"]},{"ecosystem":"NuGet","package":"Metalama.Tool","fixed_in":["2026.1.19","2025.1.18","2026.0.25"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Framework","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.1.0-preview"},{"fixed":"2026.1.19"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Tool","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.1.0-preview"},{"fixed":"2026.1.19"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Framework","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2025.1.18"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Tool","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2025.1.18"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Tool","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.0.0-preview"},{"fixed":"2026.0.25"}]}]},{"source":"ghsa","ecosystem":"NuGet","package":"Metalama.Framework","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.0.0-preview"},{"fixed":"2026.0.25"}]}]},{"source":"osv","ecosystem":"NuGet","package":"Metalama.Framework","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.1.0-preview"},{"fixed":"2026.1.19"}]}],"versions":["2026.1.0-preview","2026.1.1-preview","2026.1.10-preview","2026.1.11-preview","2026.1.12-preview","2026.1.13-preview","2026.1.14-rc","2026.1.15-rc","2026.1.16","2026.1.17","2026.1.18","2026.1.2-preview","2026.1.3-preview","2026.1.4-preview","2026.1.5-preview","2026.1.6-preview","2026.1.7-preview","2026.1.8-preview","2026.1.9-preview"]},{"source":"osv","ecosystem":"NuGet","package":"Metalama.Tool","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2026.1.0-preview"},{"fixed":"2026.1.19"}]}],"versions":["2026.1.0-preview","2026.1.1-preview","2026.1.10-preview","2026.1.11-preview","2026.1.12-preview","2026.1.13-preview","2026.1.14-rc","2026.1.15-rc","2026.1.16","2026.1.17","2026.1.18","2026.1.2-preview","2026.1.3-preview","2026.1.4-preview","2026.1.5-preview","2026.1.6-preview","2026.1.7-preview","2026.1.8-preview","2026.1.9-preview"]},{"source":"osv","ecosystem":"NuGet","package":"Metalama.Framework","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2025.1.18"}]}],"versions":["0.5.0-preview","0.5.1-preview","0.5.10-preview","0.5.11-preview","0.5.12-preview","0.5.13-preview","0.5.15-preview","0.5.16-preview","0.5.17-preview","0.5.18-preview","0.5.19-preview","0.5.2-preview","0.5.20-preview","0.5.21-preview","0.5.22-preview","0.5.23-preview","0.5.24-preview","0.5.25-preview","0.5.26-preview","0.5.27-preview","0.5.28-preview","0.5.29-preview","0.5.3-preview","0.5.30-preview","0.5.31-preview","0.5.32-preview","0.5.33-preview","0.5.34-preview","0.5.35-preview","0.5.36-preview","0.5.37-preview","0.5.38-preview","0.5.39-preview","0.5.4-preview","0.5.40-preview","0.5.41-preview","0.5.42-preview","0.5.43-preview","0.5.44-preview","0.5.45-preview","0.5.46-preview","0.5.47-preview","0.5.48-preview","0.5.49-preview","0.5.5-preview","0.5.50-preview","0.5.51-preview","0.5.52-preview","0.5.53-preview","0.5.54-preview","0.5.55-preview","0.5.56-preview","0.5.57-preview","0.5.58-preview","0.5.59-preview","0.5.6-preview","0.5.60-preview","0.5.61-preview","0.5.62-preview","0.5.63-preview","0.5.64-preview","0.5.65-preview","0.5.66-preview","0.5.67-preview","0.5.68-preview","0.5.69-preview","0.5.7-preview","0.5.70-preview","0.5.71-preview","0.5.72-preview","0.5.73-preview","0.5.74-preview","0.5.75-preview","0.5.76-preview","0.5.77-preview","0.5.78-preview","0.5.79-preview","0.5.8-preview","0.5.80-preview","0.5.81-preview","0.5.82-preview","0.5.83-preview","0.5.9-preview","2023.0.101-rc","2023.0.102-rc","2023.0.103-rc","2023.0.104-rc","2023.0.105-rc","2023.0.106-rc","2023.0.107-rc","2023.0.108-rc","2023.0.109-rc","2023.0.110-rc","2023.0.111-rc","2023.0.112-rc","2023.0.113-rc","2023.0.114","2023.0.115","2023.0.116","2023.0.117","2023.0.118","2023.0.119","2023.0.120","2023.0.121","2023.1.1-preview","2023.1.10","2023.1.11","2023.1.12","2023.1.2-preview","2023.1.3-preview","2023.1.4-preview","2023.1.5-preview","2023.1.6-rc","2023.1.7-rc","2023.1.8-rc","2023.1.9","2023.2.1-preview","2023.2.2-rc","2023.2.3-rc","2023.2.4","2023.2.5","2023.3.1-preview","2023.3.10","2023.3.2-preview","2023.3.3-preview","2023.3.4-preview","2023.3.5-rc","2023.3.6-rc","2023.3.7-rc","2023.3.8","2023.3.9","2023.4.1-preview","2023.4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Local code execution via DLL planting in world-writable temporary directories (Linux/macOS)","description":"Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.","status":"published","published":"2026-10-30T20:23:50.882Z","modified":"2026-10-30T22:13:12.107Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-377","CWE-427"],"updated_at":"2026-11-02T14:20:14.999906Z"}],"euvd":[{"id":"EUVD-2026-114452","description":"Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.","status":"published","published":"2026-10-30T20:23:50Z","modified":"2026-10-30T22:13:12Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-02T16:59:01.632804Z"}],"ghsa":[{"id":"GHSA-m6wq-39m7-9xpp","title":"Metalama allows local code execution through DLL planting in shared temporary directories","description":"## Summary\n\nMetalama loaded and executed compile-time assemblies, auxiliary executable tools, and embedded helper assemblies from predictable temporary directories. On Linux and macOS the default cache location was the world-writable system temporary directory (`Path.GetTempPath()`, i.e. `/tmp`), and previously-generated artifacts were trusted based on the presence of a sentinel/`.completed` marker file rather than on any integrity verification.\n\nA local, unprivileged user on a shared machine or CI/build agent can pre-create the deterministic cache directory structure and plant a malicious DLL together with the matching sentinel file. When a higher-privileged user (or build/service account) subsequently runs a build, Metalama finds the sentinel, skips regeneration, and loads and executes the attacker-supplied assembly inside the compiler / IDE / MSBuild process.\n\nAffected load-and-execute paths:\n- the cache of compile-time assemblies that Metalama generates from your aspects;\n- auxiliary executable tools that Metalama extracts to a local directory and then launches;\n- embedded .NET helper assemblies that Metalama extracts to a local directory and loads into the build / IDE process.\n\n## Impact\n\nArbitrary code execution in the security context of the building user — i.e. a local privilege escalation across user accounts on shared POSIX systems (multi-user developer machines, CI/build agents). The attacker obtains code execution as the victim without holding the victim's privileges, and can read source/secrets, tamper with build output (supply-chain injection), or disrupt builds.\n\n## Affected configurations\n\n- **Linux and macOS, default configuration — affected.** The shipped default uses the world-writable system temp directory.\n- **Windows, default configuration — not affected.** The default per-user temporary directory is protected by OS ACLs, so cross-user planting is not possible.\n- The `METALAMA_TEMP` environment variable is a deployer-controlled override and is **out of scope**: pointing it at an insecure (e.g. world-writable or attacker-owned) location is a deployment misconfiguration, not a defect in the product.\n\n## Severity\n\nCVSS v3.1: `AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H` = **8.2 (High)** for the affected POSIX default configuration (Scope:Changed reflects the cross-user privilege escalation).\n\nCVSS v4.0 cross-check: `CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:L/VI:H/VA:L/SC:L/SI:H/SA:H` = 6.0 (Medium), which more granularly attributes low impact to the cache itself and high impact to the subsequent build process. The honest range is therefore Medium-High depending on the scoring model and platform.\n\n## Fix\n\nCaches and extraction directories were relocated from the world-writable system temp directory to per-user application-data locations (`$XDG_CACHE_HOME` / `~/.cache/Metalama` on POSIX), relying on OS-enforced per-user ownership as the trust boundary. Fixed in **2026.1.19**.\n\n## Weaknesses\n\n- CWE-377: Insecure Temporary File\n- CWE-427: Uncontrolled Search Path Element\n\n## Affected packages\n\n- Metalama.Framework \u003c 2026.1.19, \n- Metalama.Tool \u003c 2026.1.19\n\nInternal tracking: metalama/Metalama#1650.","status":"published","published":"2026-10-14T19:24:53Z","modified":"2026-10-14T19:24:55Z","cvss":[{"version":"4.0","score":6,"vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:L/VI:H/VA:L/SC:L/SI:H/SA:H","level":"medium"},{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-377","CWE-427"],"updated_at":"2026-11-02T14:41:31.175024Z"}],"nvd":[{"id":"CVE-2026-62847","description":"Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.","status":"published","published":"2026-10-30T21:17:13.807Z","modified":"2026-11-02T19:35:33.347Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-377","CWE-427"],"updated_at":"2026-11-03T00:02:42.364722Z"}],"osv":[{"id":"CVE-2026-62847","title":"Metalama: Local code execution via DLL planting in world-writable temporary directories (Linux/macOS)","description":"Metalama is a Roslyn-based open-source patterns and architecture toolkit for C#. Prior to 2025.1.18, 2026.0.25 and 2026.1.19, Metalama.Framework and Metalama.Tool load and execute compile-time assemblies, auxiliary executable tools and embedded helper assemblies from predictable temporary directories. On `Linux` and `macOS`, the default `Path.GetTempPath()` location is world-writable, and existing artifacts are trusted based on sentinel or `.completed` marker files rather than integrity verification. A local unprivileged user on a shared machine or CI/build agent can pre-create the deterministic directory structure and plant a malicious DLL with the matching sentinel. When a higher-privileged developer or build account subsequently builds, Metalama skips regeneration and executes the planted artifact in the compiler, IDE or MSBuild process as the building user. This permits cross-user privilege escalation, reading source and secrets, supply-chain tampering with build output, or disrupting builds. Default Windows per-user temporary directories are protected by ACLs and are not affected. Deployer-selected insecure cache locations are outside the vulnerability's scope. This issue is fixed in versions 2025.1.18, 2026.0.25 and 2026.1.19.","status":"published","published":"2026-10-30T20:23:50.882Z","modified":"2026-11-04T02:30:19.365879902Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-377","CWE-427"],"updated_at":"2026-11-07T03:08:08.334472Z"},{"id":"GHSA-m6wq-39m7-9xpp","title":"Metalama allows local code execution through DLL planting in shared temporary directories","description":"## Summary\n\nMetalama loaded and executed compile-time assemblies, auxiliary executable tools, and embedded helper assemblies from predictable temporary directories. On Linux and macOS the default cache location was the world-writable system temporary directory (`Path.GetTempPath()`, i.e. `/tmp`), and previously-generated artifacts were trusted based on the presence of a sentinel/`.completed` marker file rather than on any integrity verification.\n\nA local, unprivileged user on a shared machine or CI/build agent can pre-create the deterministic cache directory structure and plant a malicious DLL together with the matching sentinel file. When a higher-privileged user (or build/service account) subsequently runs a build, Metalama finds the sentinel, skips regeneration, and loads and executes the attacker-supplied assembly inside the compiler / IDE / MSBuild process.\n\nAffected load-and-execute paths:\n- the cache of compile-time assemblies that Metalama generates from your aspects;\n- auxiliary executable tools that Metalama extracts to a local directory and then launches;\n- embedded .NET helper assemblies that Metalama extracts to a local directory and loads into the build / IDE process.\n\n## Impact\n\nArbitrary code execution in the security context of the building user — i.e. a local privilege escalation across user accounts on shared POSIX systems (multi-user developer machines, CI/build agents). The attacker obtains code execution as the victim without holding the victim's privileges, and can read source/secrets, tamper with build output (supply-chain injection), or disrupt builds.\n\n## Affected configurations\n\n- **Linux and macOS, default configuration — affected.** The shipped default uses the world-writable system temp directory.\n- **Windows, default configuration — not affected.** The default per-user temporary directory is protected by OS ACLs, so cross-user planting is not possible.\n- The `METALAMA_TEMP` environment variable is a deployer-controlled override and is **out of scope**: pointing it at an insecure (e.g. world-writable or attacker-owned) location is a deployment misconfiguration, not a defect in the product.\n\n## Severity\n\nCVSS v3.1: `AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H` = **8.2 (High)** for the affected POSIX default configuration (Scope:Changed reflects the cross-user privilege escalation).\n\nCVSS v4.0 cross-check: `CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:L/VI:H/VA:L/SC:L/SI:H/SA:H` = 6.0 (Medium), which more granularly attributes low impact to the cache itself and high impact to the subsequent build process. The honest range is therefore Medium-High depending on the scoring model and platform.\n\n## Fix\n\nCaches and extraction directories were relocated from the world-writable system temp directory to per-user application-data locations (`$XDG_CACHE_HOME` / `~/.cache/Metalama` on POSIX), relying on OS-enforced per-user ownership as the trust boundary. Fixed in **2026.1.19**.\n\n## Weaknesses\n\n- CWE-377: Insecure Temporary File\n- CWE-427: Uncontrolled Search Path Element\n\n## Affected packages\n\n- Metalama.Framework \u003c 2026.1.19, \n- Metalama.Tool \u003c 2026.1.19\n\nInternal tracking: metalama/Metalama#1650.","status":"published","published":"2026-10-14T19:24:53Z","modified":"2026-10-14T19:30:07.066808149Z","cvss":[{"version":"3.1","score":8.2,"vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H","level":"high"},{"version":"4.0","score":6,"vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:P/VC:L/VI:H/VA:L/SC:L/SI:H/SA:H","level":"medium"}],"cwes":["CWE-377","CWE-427"],"updated_at":"2026-11-02T15:46:51.463834Z"}]}}