All vulnerabilities
CVE-2026-114134GHSA-cg8m-r9f2-5wm2

Black: GitHub Action installs unvalidated required-version from pyproject.toml

blackpipLibraries & packages
Open in ThreatlineRecord JSON
CVSS
8.7High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)No scoreNo FIRST EPSS score in this snapshot yet
Fixed in26.10.1Fixed versionGitHub
Published22 Oct 2026Updated 22 Oct 2026GitHub

What fixes it

  • 26.10.1black, pipGitHub
  • 26.10.1black, PyPIOSVpip install "black>=26.10.1"

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

Summary

The GitHub Action bundled with Black can read the version from tool.black.required-version if use_pyproject is set to True. This version is not validated and therefore can be used to execute untrusted code in the context of a victim's repository.

Details

This is similar to the previous CVE-2026-31900. The value in tool.black.required-version is accepted as the version to be installed by the action without validation.

Proof of concept

Reproduction requires a victim to use Black's GitHub Action with use_pyproject: true. The attacker would then issue a PR to the victim's repository with pyproject.toml edited so that Black points to a malicious repository.

Impact

This is a remote code execution vulnerability impacting users using the GitHub Action bundled with psf/black and using the use_pyproject: true setting.

Text from GitHub Advisory Database

Affected versions 52

  • black, pip< 26.10.1GitHub
  • black, PyPIfrom first release, fixed in 26.10.1OSV
  • black, PyPI18.3a0OSV
  • black, PyPI18.3a1OSV
  • black, PyPI18.3a2OSV
  • black, PyPI18.3a3OSV
  • black, PyPI18.3a4OSV
  • black, PyPI18.4a0OSV
  • black, PyPI18.4a1OSV
  • black, PyPI18.4a2OSV
  • black, PyPI18.4a3OSV
  • black, PyPI18.4a4OSV
  • black, PyPI18.5b0OSV
  • black, PyPI18.5b1OSV
  • black, PyPI18.6b0OSV
  • black, PyPI18.6b1OSV
  • black, PyPI18.6b2OSV
  • black, PyPI18.6b3OSV
  • black, PyPI18.6b4OSV
  • black, PyPI18.9b0OSV
  • black, PyPI19.10b0OSV
  • black, PyPI19.3b0OSV
  • black, PyPI20.8b0OSV
  • black, PyPI20.8b1OSV
  • black, PyPI21.10b0OSV
  • black, PyPI21.11b0OSV
  • black, PyPI21.11b1OSV
  • black, PyPI21.12b0OSV
  • black, PyPI21.4b0OSV
  • black, PyPI21.4b1OSV
  • black, PyPI21.4b2OSV
  • black, PyPI21.5b0OSV
  • black, PyPI21.5b1OSV
  • black, PyPI21.5b2OSV
  • black, PyPI21.6b0OSV
  • black, PyPI21.7b0OSV
  • black, PyPI21.8b0OSV
  • black, PyPI21.9b0OSV
  • black, PyPI22.1.0OSV
  • black, PyPI22.10.0OSV
  • black, PyPI22.12.0OSV
  • black, PyPI22.3.0OSV
  • black, PyPI22.6.0OSV
  • black, PyPI22.8.0OSV
  • black, PyPI23.1.0OSV
  • black, PyPI23.10.0OSV
  • black, PyPI23.10.1OSV
  • black, PyPI23.11.0OSV
  • black, PyPI23.12.0OSV
  • black, PyPI23.12.1OSV
  • black, PyPI23.1a1OSV
  • black, PyPI23.3.0OSV

References 5