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.
CVE-2026-31900
CRITICALNVD 9.89.8
EchelonGraph scoreLOW confidence
This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: nvd
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.8
- EG Score
- 9.8(low)
- EG Risk
- 49(Track)EG Risk 49/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity98% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 38%
- KEV
- Not listed
Published
March 11, 2026
Last Modified
June 17, 2026
Advisory Details (2)
Auto-updated Jul 27, 2026Patch available. Sources: github_commit, github.
github Patch Available
Vulnerable version parsing leads to RCE in GitHub Action · Advisory · psf/black · GitHub
https://github.com/psf/black/security/advisories/GHSA-v53h-f6m7-xcgmgithub_commit
commit 0a2560b98136 (psf/black)
Fix landed in psf/black commit 0a2560b98136 — awaiting tagged release
https://github.com/psf/black/commit/0a2560b981364dde4c8cf8ce9d164c40669a8611Affected Packages
(1 across 1 ecosystem)
PyPI(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| black | 18.3a0 ... 26.1a1 (69 versions) | 26.3.0 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 5× in last 7d / 5× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-01 04:16 UTCEPSS rescore
- 2026-07-30 16:28 UTCEPSS rescore
- 2026-07-30 01:30 UTCEPSS rescore
- 2026-07-28 15:36 UTCEPSS rescore
- 2026-07-27 13:41 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-20
- CVE-2005-0050EG 10.0EPSS p99HIGH
- CVE-2004-1019EG 10.0EPSS p94HIGH
- CVE-2004-0840EG 10.0EPSS p98HIGH
- CVE-2003-1425EG 10.0EPSS p96HIGH
- CVE-2003-1487EG 10.0EPSS p94HIGH
- CVE-2002-1874EG 10.0HIGH
- CVE-2002-2236EG 10.0EPSS p91HIGH
- CVE-2002-2365EG 10.0HIGH
- CVE-2002-1358EG 10.0EPSS p92HIGH
- CVE-2002-1359EG 10.0EPSS p100HIGH
Frequently asked(5)
What is CVE-2026-31900?
CVE-2026-31900 is a critical vulnerability published on March 11, 2026. 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…
When was CVE-2026-31900 disclosed?
CVE-2026-31900 was first published in the National Vulnerability Database on March 11, 2026, with the most recent update on June 17, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-31900 actively exploited?
CVE-2026-31900 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 62.4% of all scored CVEs.
What is the CVSS score of CVE-2026-31900?
CVE-2026-31900 has a CVSS v3 base score of 9.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-31900?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-31900, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-31900
Is Your Infrastructure Affected by CVE-2026-31900?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.