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CVE-2026-31900 — Vulnerability in black — CVE Details

CRITICAL

Published March 11, 2026Updated July 13, 2026Source: osv

Summary

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.

Advisory Timeline

  • First published March 11, 2026 (215 days ago).
  • Last revised July 13, 2026 — 123 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

pip
Update black to 26.3.0 or later
pip install "black>=26.3.0"

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: pypi (1).

PackageEcosystemAffectedFixed In
black
pypi
18.3a0, 18.3a1, 18.3a2, 18.3a3 (+65 more)26.3.0

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.8 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

Frequently Asked Questions

What is CVE-2026-31900?
This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.8/10).
How do I check if my project is affected by CVE-2026-31900?
CVE-2026-31900 affects black. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-31900 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.8

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

PYSEC-2026-2120
GHSA-v53h-f6m7-xcgm

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