CVE-2026-31900
Black's vulnerable version parsing leads to RCE in GitHub Action
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.
INFO
Published Date :
March 11, 2026, 8:16 p.m.
Last Modified :
March 16, 2026, 8:02 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Black to version 26.3.0 or newer.
- Review and audit pyproject.toml configurations.
- Disable use_pyproject option if not needed.
- Pin Black action version to a trusted release.
Public PoC/Exploit Available at Github
CVE-2026-31900 has a 4 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-31900.
| URL | Resource |
|---|---|
| https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611 | Patch |
| https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm | Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-31900 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-31900
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-31900 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-31900 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Mar. 16, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Added CWE NVD-CWE-noinfo Added CPE Configuration OR *cpe:2.3:a:python:black:*:*:*:*:*:*:*:* versions up to (excluding) 26.3.0 Added Reference Type GitHub, Inc.: https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm Types: Mitigation, Vendor Advisory -
New CVE Received by [email protected]
Mar. 11, 2026
Action Type Old Value New Value Added 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. Added CVSS V4.0 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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-20 Added Reference https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611 Added Reference https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgm