VulnerabilityAnalyzed

CVE-2026-31900

A malicious pull request could edit pyproject.toml to use a direct URL reference to a malicious repository.

HIGH 8.7EPSS 0.46%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.46%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

Description

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 4.0: 8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.46% probability · 39th percentile
CISA KEV: Not listed
Weakness: CWE-20
Affected: python/black
Source: security-advisories@github.com

References

https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611Patch
https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgmMitigation, Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.