Vulnerability · Published Oct 30, 2026 · Assigned by GitHub_M
CVE-2026-62847Metalama: Local code execution via DLL planting in world-writable temporary directories (Linux/macOS)
High 8.2
In plain English
A high-severity uncontrolled search path in Metalama from metalama. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| NuGet | metalama.framework | 2026.1.19 | GHSA-m6wq-39m7-9xpp |
| NuGet | metalama.framework | 2025.1.18 | GHSA-m6wq-39m7-9xpp |
| NuGet | metalama.framework | 2026.0.25 | GHSA-m6wq-39m7-9xpp |
| NuGet | metalama.tool | 2026.1.19 | GHSA-m6wq-39m7-9xpp |
| NuGet | metalama.tool | 2025.1.18 | GHSA-m6wq-39m7-9xpp |
| NuGet | metalama.tool | 2026.0.25 | GHSA-m6wq-39m7-9xpp |
Affected products (as reported)
Weakness: CWE-377, CWE-427 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
References
- https://github.com/metalama/Metalama/security/advisories/GHSA-m6wq-39m7-9xpp x_refsource_CONFIRM
- https://github.com/metalama/Metalama/pull/1650 x_refsource_MISC
- https://github.com/metalama/Metalama/commit/09911349a916e82194b1cfaa6d0a38acad928fc9 x_refsource_MISC
- https://github.com/metalama/Metalama/commit/92c4feecfce86d18fcb007ab6d3a1b4383326a2e x_refsource_MISC
- https://github.com/metalama/Metalama/releases/tag/release/2025.1.18 x_refsource_MISC
- https://github.com/metalama/Metalama/releases/tag/release/2026.0.25 x_refsource_MISC
- https://github.com/metalama/Metalama/releases/tag/release/2026.1.19 x_refsource_MISC