CVE Tools
Sign in

CVE-2026-31900

Black's vulnerable version parsing leads to RCE in GitHub Action

Published: Mar 11, 2026Updated: Mar 16, 2026 Sources: CVE List NVD GHSACWE-20
9.8CRITICAL
NVD MITRE
EPSS Score
0.5%
Top 63.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-20NVD-CWE-noinfo

Affected Products

python
oss-project·US
black
OSS Libraries
GitHub Actions
commercial·US
psf/blackSaaS
DevTools & CI / ci-cd
psf
oss-project
blackLibrary
OSS Libraries / generic-library

Exploitability

Official Patch Available
Workaround Available
Is your org exposed to CVE-2026-31900?We can run the check for you — a free external exposure review, no install. Check my exposure

Attack Graph

Products CVE Techniques Tactics

Click technique nodes for MITRE ATT&CK details · drag to pan · Ctrl/⌘ + scroll to zoom, or go fullscreen.

MITRE ATT&CK

1 technique
Initial Access
View detailed technique mapping

References

https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611
github.com
https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm
github.com
https://nvd.nist.gov/vuln/detail/CVE-2026-31900
nvd.nist.gov
and 1 more references View all →
News mentions
Could not load news mentions.

Unlock Complete Vulnerability Intelligence

Get the full picture for CVE-2026-31900 and every CVE in our database. Create a free account — no credit card required.

Create Free Account
Plain-language analysis
Impact assessment and exploitation scenario in plain English
Attack graph visualization
Interactive attack path and kill chain mapping
Exploit details & PoC links
ExploitDB, Metasploit, GitHub PoCs with direct links
Nuclei scanner templates
Ready-to-use vulnerability scanner templates
Full remediation guide
Patch instructions, workarounds, and compliance impact
Interactive AI chat
Ask questions about this vulnerability in natural language
Related vulnerabilities
Semantically similar CVEs and attack patterns
REST API & MCP access
Integrate vulnerability data into your workflows