GitHub Advisoryadvisory · GitHub Actions

GHSA-v53h-f6m7-xcgm Black's vulnerable version parsing leads to RCE in GitHub Action

HIGH Published 2026-03-07 Modified 2026-03-11 Official page ↗
Aliases
CVE-2026-31900
Ecosystem
GitHub Actions
Packages
psf/black
Severity
High
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weaknesses
CWE-20
Reviewed
2026-03-07

Affected packages

• GitHub Actions psf/black: < 26.3.0 → fixed in 26.3.0

Description

Impact Black provides a GitHub action for formatting code. This action supports an option, `use_pyproject: true`, for reading the version of Black to use from the repository `pyproject.toml`. A malicious pull request could edit pyproject.toml to use a direct URL reference to a malicious repository. This could lead to arbitrary code execution in the context of the GitHub Action. Attackers could then gain access to secrets or permissions available in the context of the action. Patches Version 26.3.0 fixes this vulnerability by tightening the validation of the `version` field. Users who use the GitHub Action as `psf/black@stable` will automatically pick up this update. Workarounds Do not use the `use_pyproject: true` option in the psf/black GitHub Action.

Related

Alias · CVE (1)

  • CVE-2026-31900 Black is the uncompromising Python code formatter. vulnerability

Weakness · CWE (1)

  • CWE-20 Improper Input Validation weakness

References