9.8

CVE-2026-31900: psf black Improper Input Validation

CVSS: 9.8v3.1CriticalAnalyzed
AliasesPYSEC-2026-2120GHSA-v53h-f6m7-xcgmUBUNTU-CVE-2026-31900
Published 11-03-2026Last modified 13-03-2026
Open JSON

Vulnerability summary

CVE-2026-31900 is a critical (CVSS 9.8) Improper Input Validation vulnerability in psf black. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 50.6% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (NVD)
EPSS score
0.66%
0%100%
Low · +0.20 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 3
OPENSUSE-SU-2026:10372-1OPENSUSE-SU-2026:20417-1SUSE-SU-2026:20928-1

Timeline

  1. 11-03-2026
    PublishedVulnerability first disclosed.
  2. 13-03-2026
    Last modifiedVulnerability information updated.

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 metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.66%

Chance of exploitation in the next 30 days

Percentile

51%

Versus all other CVEs

30-day change

+0.20 pp

From 0.46% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.66%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • blackAll versions (No fix recorded)
Psf1 product
PyPI1 product
  • black< 26.3.0
Python1 product
Ubuntu1 product
  • blackAll versions (No fix recorded)

5 vendors · 5 products

References

5 links