PT-2026-114418 · Nuget · Metalama.Framework+1

CVE-2026-62847

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Published

2026-10-14

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Updated

2026-10-14

CVSS v3.1

8.2

High

VectorAV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

Summary

Metalama 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.
A 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.
Affected load-and-execute paths:
  • the cache of compile-time assemblies that Metalama generates from your aspects;
  • auxiliary executable tools that Metalama extracts to a local directory and then launches;
  • embedded .NET helper assemblies that Metalama extracts to a local directory and loads into the build / IDE process.

Impact

Arbitrary 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.

Affected configurations

  • Linux and macOS, default configuration — affected. The shipped default uses the world-writable system temp directory.
  • Windows, default configuration — not affected. The default per-user temporary directory is protected by OS ACLs, so cross-user planting is not possible.
  • 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.

Severity

CVSS 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).
CVSS 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.

Fix

Caches 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.

Weaknesses

  • CWE-377: Insecure Temporary File
  • CWE-427: Uncontrolled Search Path Element

Affected packages

  • Metalama.Framework < 2026.1.19,
  • Metalama.Tool < 2026.1.19
Internal tracking: metalama/Metalama#1650.

Fix

Uncontrolled Search Path Element

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Weakness Enumeration

CWE-427CWE-377

Related Identifiers

CVE-2026-62847
GHSA-M6WQ-39M7-9XPP

Affected Products

Metalama.Framework
Metalama.Tool