GHSA-CG8M-R9F2-5WM2
Vulnerability from github – Published: 2026-10-22 16:18 – Updated: 2026-10-22 16:18Summary
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": [
{
"package": {
"ecosystem": "PyPI",
"name": "black"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "26.10.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-114134"
],
"database_specific": {
"cwe_ids": [
"CWE-829"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-22T16:18:57Z",
"nvd_published_at": null,
"severity": "HIGH"
},
"details": "### Summary\n\nThe 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\u0027s repository.\n\n### Details\n\nThis 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.\n\n### Proof of concept\n\nReproduction requires a victim to use Black\u0027s GitHub Action with `use_pyproject: true`. The attacker would then issue a PR to the victim\u0027s repository with `pyproject.toml` edited so that Black points to a malicious repository.\n\n### Impact\n\nThis is a remote code execution vulnerability impacting users using the GitHub Action bundled with psf/black and using the `use_pyproject: true` setting.",
"id": "GHSA-cg8m-r9f2-5wm2",
"modified": "2026-10-22T16:18:57Z",
"published": "2026-10-22T16:18:57Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/psf/black/security/advisories/GHSA-cg8m-r9f2-5wm2"
},
{
"type": "WEB",
"url": "https://github.com/psf/black/pull/5510"
},
{
"type": "WEB",
"url": "https://github.com/psf/black/commit/ac1f71563aeccf73cf13ece00f231d9d6c66a514"
},
{
"type": "PACKAGE",
"url": "https://github.com/psf/black"
},
{
"type": "WEB",
"url": "https://github.com/psf/black/releases/tag/26.10.1"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Black: GitHub Action installs unvalidated required-version from pyproject.toml"
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.