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Fencer Vulns
high 8.2

CVE-2026-62847 json

Metalama: Local code execution via DLL planting in world-writable temporary directories (Linux/macOS)

published 2026-10-14 25 d ago modified 2026-11-02 6 d ago also GHSA-m6wq-39m7-9xpp , EUVD-2026-114452

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

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.

Patch / fix

  • nuget Metalama.Framework 2025.1.18, 2026.0.25, 2026.1.19
  • nuget Metalama.Tool 2025.1.18, 2026.0.25, 2026.1.19

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
9 d ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
GitHub 3.1 8.2 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
nuget Metalama.Framework
>=2026.1.0-preview, <2026.1.19
<2025.1.18
>=2026.0.0-preview, <2026.0.25
2026.1.19
2025.1.18
2026.0.25
nuget Metalama.Tool
>=2026.1.0-preview, <2026.1.19
<2025.1.18
>=2026.0.0-preview, <2026.0.25
2026.1.19
2025.1.18
2026.0.25

Affected products

  • metalama Metalama

Classification

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

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.