# CVE-2026-114134: Black GitHub Action code injection via unvalidated required-version

Source: https://junglewise.ai/threats/cve-2026-114134-black-github-action-installs-unvalidated-required-version-from  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-05. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

CVE-2026-114134 · Severity: high · CVSS 4 · Published 2026-11-05

Black is a popular Python code formatter. Its bundled GitHub Action, when configured with the use_pyproject setting enabled, accepts package version specifications from pyproject.toml without validation. An attacker can modify this file in a pull request to point to a malicious code repository, allowing arbitrary code execution in the victim's CI/CD workflow.

Technologies: [black (PyPI)](https://junglewise.ai/threats/technologies/pypi-black). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi), [Python Software Foundation](https://junglewise.ai/threats/vendors/python-software-foundation).

## Quick answers

**Is CVE-2026-114134 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-114134 being exploited in the wild.

**How severe is CVE-2026-114134?** High severity, with a CVSS score of 4, published 5 November 2026.

**Which products and versions are affected?** black (PyPI) < 26.10.1, ECOSYSTEM:introduced=0,fixed=26.10.1; Python Software Foundation Black < 26.10.1.

**Is there a fix for CVE-2026-114134?** Yes. black (PyPI): upgrade to 26.10.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-114134 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-114134?** Check whether you run black (PyPI) or Python Software Foundation Black at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- black (PyPI): upgrade to 26.10.1 or later

  ```sh
  pip install "black>=26.10.1"
  ```


## Technical details

The Black GitHub Action fails to validate the tool.black.required-version field when use_pyproject is set to True, allowing arbitrary Python package installation from attacker-controlled repositories. An attacker with write access to a repository (or via a crafted pull request) can modify pyproject.toml to inject a malicious version string that pip will install without restrictions. This grants remote code execution in the GitHub Actions runner context with the privileges of the workflow.

## Affected products

- Python Software Foundation Black < 26.10.1

## Identifiers

- CVE-2026-114134
- GHSA-cg8m-r9f2-5wm2

## Timeline

- 2026-10-22: disclosed
- 2026-10-22: advisory

## References

- [https://api.github.com/users/jiteshgulati](https://api.github.com/users/jiteshgulati)

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