Summary
Black: GitHub Action installs unvalidated required-version from pyproject.toml
The GitHub Action bundled with Black can read the version from tool.black.required-version if use_pyproject is set to True. This version is not validated and therefore can be used to execute untrusted code in the context of a victim's repository.
Details
This is similar to the previous CVE-2026-31900. The value in tool.black.required-version is accepted as the version to be installed by the action without validation.
Proof of concept
Reproduction requires a victim to use Black's GitHub Action with use_pyproject: true. The attacker would then issue a PR to the victim's repository with pyproject.toml edited so that Black points to a malicious repository.
Impact
This is a remote code execution vulnerability impacting users using the GitHub Action bundled with psf/black and using the use_pyproject: true setting.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-114134? CVE-2026-114134 is a high-severity security vulnerability in black (pip), affecting versions < 26.10.1. It is fixed in 26.10.1.
- Which versions of black are affected by CVE-2026-114134? black (pip) versions < 26.10.1 is affected.
- Is there a fix for CVE-2026-114134? Yes. CVE-2026-114134 is fixed in 26.10.1. Upgrade to this version or later.
- Is CVE-2026-114134 exploitable, and should I be worried? Whether CVE-2026-114134 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-114134 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-114134? Upgrade
blackto 26.10.1 or later.