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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.

PUBLISHED Reserved 2026-03-09 | Published 2026-03-11 | Updated 2026-03-13 | Assigner GitHub_M




HIGH: 8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Problem types

CWE-20: Improper Input Validation

Product status

< 26.3.0
affected

References

github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm

github.com/...ommit/0a2560b981364dde4c8cf8ce9d164c40669a8611

cve.org (CVE-2026-31900)

nvd.nist.gov (CVE-2026-31900)

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