High 8.7Published Mar 11, 2026

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

Updated under an hour ago (Oct 27, 2026, 7:20 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for psf black

Exploited in the last 30 days

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.

CVSS: 8.7 HIGH (v4.0, CNA)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
Weakness (CWE): CWE-20
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 12, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

psf black psf:black (from the name)	before 26.3.0	CNA record
python black python:black	before 26.3.0	NVD

References

References

https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm	x-refsource-confirm, mitigation, vendor-advisory
https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611	x-refsource-misc, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.