Vulnerability · Published Nov 5, 2026 · Assigned by GitHub_M

CVE-2026-114134Black: GitHub Action installs unvalidated required-version from pyproject.toml

High 8.7

In plain English

A high-severity security flaw in black from psf. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.7High

Exploit odds (30 days)0.4%top 65.2% of all CVEs

Exploited in the wildNo reportsnot in CISA KEV

Attack toolingNoneno public tooling known

Official description

Black is the uncompromising Python code formatter. Prior to 26.10.1, the Black GitHub Action with use_pyproject: true accepts tool.black.required-version from pyproject.toml without validating that it is a released Black version specifier. An attacker who can submit a pull request can change that field to a direct reference to attacker-controlled code, causing the workflow to install and execute the code in the victim repository's GitHub Actions context. This issue is fixed in version 26.10.1.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	black	26.10.1	GHSA-cg8m-r9f2-5wm2

Affected products (as reported)

Vendor	Product	Versions
psf	black	< 26.10.1

Weakness: CWE-829 · 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

References

https://github.com/psf/black/security/advisories/GHSA-cg8m-r9f2-5wm2 x_refsource_CONFIRM
https://github.com/psf/black/pull/5510 x_refsource_MISC
https://github.com/psf/black/commit/ac1f71563aeccf73cf13ece00f231d9d6c66a514 x_refsource_MISC