CVE-2026-31900 HIGH

CVE-2026-31900: Black's vulnerable version parsing leads to RCE in GitHub Action

Vendor Psf
Product black
Weakness CWE-20 · Input validation
Published March 11, 2026
Last update March 13, 2026

CVSS base score

8.7/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality
Integrity

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

What the vulnerability does

01Description

Black is the uncompromising Python code formatter. 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. Version 26.3.0 fixes this vulnerability.

Key dates

02Disclosure timeline

March 11, 2026 CVE published
March 13, 2026 Record updated

Related vulnerabilities

04Related CVE