CVE-2026-62847

HighCVSS 8.2

Published: 30/10/2026(UTC)Updated: 02/11/2026(UTC)Translated: 30/10/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.15%

4th percentile - higher than 4% of all known CVEs

Summary

Metalama before versions 2025.1.18, 2026.0.25, and 2026.1.19 loads and executes compile-time assemblies from predictable temporary directories, trusting existing artifacts based on marker files. On Linux and macOS, the temporary directory is world-writable, allowing a local unprivileged user to pre-create the directory structure and plant a malicious DLL. When a privileged developer or build account runs a build, Metalama executes the planted artifact in the compiler, IDE, or MSBuild process.

Risk Assessment

A local unprivileged user can escalate privileges, read source code and secrets, tamper with build output, or disrupt builds. Default Windows per-user temporary directories are protected and not affected.

Recommendation

Update Metalama to version 2025.1.18, 2026.0.25, or 2026.1.19. Avoid using shared, writable temporary directories on Linux and macOS.

Other vulnerabilities in Metalama

CVE-2026-62848High
The vulnerability in Metalama's Windows Visual Studio integration deserializes local named-pipe messages without restricting which CLR types can be instantiated. Through a pipe with a predictable name, a same-user local process can send crafted messages leading to arbitrary code execution inside the Visual Studio process. Default Windows pipe ACLs limit writers to the logged-in user, so no privilege escalation or security boundary crossing occurs.

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS