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9.4
CVE-2026-114134: Black GitHub Action can install attacker code
CVE-2026-114134 · published 3 days ago
Summary
The Black code‑formatter’s GitHub Action (when configured to read the pyproject.toml file) may accept a version string that points to any location, not just an official Black release. An attacker who can submit a pull request could change that field to load malicious code during the automated workflow. Update the Action to version 26.10.1 or later to enforce proper version checks.
What to do
- Update Łukasz langa black to version 26.10.1.
- Update black to version 26.10.1.
- Update black to version 26.10.0+aikido.1.
- Update black to version 26.5.1+aikido.1.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| pip | Łukasz langa | black |
< 26.10.1 Fix: upgrade to 26.10.1
|
| pip | – | black |
< 26.10.1 Fix: upgrade to 26.10.1
|
| Root:PyPI | – | black |
< 26.10.0+aikido.1 < 26.5.1+aikido.1 Fix: upgrade to 26.10.0+aikido.1
|
| – | psf | black | < 26.10.1 |
| Debian:12 | debian | black | All versions |
Original advisory text
Black: GitHub Action installs unvalidated required-version from pyproject.toml
Black is the uncompromising Python code formatter. Prior to 26.10.1, the Black GitHub Action with use_pyproject: true accepts tool.black.required-version from pyproject.toml without validating that it is a released Black version specifier. An attacker who can submit a pull request can change that field to a direct reference to attacker-controlled code, causing the workflow to install and execute the code in the victim repository's GitHub Actions context. This issue is fixed in version 26.10.1.
References
- https://github.com/psf/black/security/advisories/GHSA-cg8m-r9f2-5wm2 Vendor Advisory
- https://github.com/psf/black/pull/5510 Patch
- https://github.com/psf/black/releases/tag/26.10.1
- https://github.com/advisories/GHSA-cg8m-r9f2-5wm2
- https://github.com/psf/black Product
- https://github.com/psf/black/commit/ac1f71563aeccf73cf13ece00f231d9d6c66a514 Patch
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/114xxx/CVE-2026-1141... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-114134 Vendor Advisory
- https://security-tracker.debian.org/tracker/CVE-2026-114134 Vendor Advisory
Internet-facing
14 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit (estimated)
- Gives an attacker full control (estimated)
Severity
9.4
Critical
Type
CWE-829Inclusion of Functionality from Untrusted Control Sphere
Timeline
Published5 Nov 2026
Updated7 Nov 2026
First seen22 Oct 2026
Sources
GHSA-cg8m-r9f2-5wm2 · GHSA
CVE-2026-114134 · NVD
GHSA-cg8m-r9f2-5wm2 · OSV
CVE-2026-114134 · MITRE
CVE-2026-114134 · OSV
DEBIAN-CVE-2026-114134 · OSV
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