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CVE record · CVE-2026-21876

OWASP CRS has multipart bypass using multiple content-type parts

CVSS 9.3 CriticalCriticalEPSS 0.18 · 97th percentile

Critical, because:

  • CVSS score 9.3: 9.0 or more.
  • CVSS score 9.3 (7.0 or more) and EPSS 0.18 (0.1 or more): a high score and a real chance of exploitation in the next 30 days.

How we decide what’s critical

Published by the CVE Program (CNA: GitHub_M) at 8 Jan 2026, 13:55 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
VendorProductVersions
coreruleset coreruleset
  • affected < 4.22.0
  • affected < 3.3.8
Identifiers
CVE-2026-21876
CNA
GitHub_M
Weakness (CWE)
CWE-794
Tags
Published
8 Jan 2026
Updated
9 Apr 2026

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.3 Critical 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.18, the 97th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 8 Jan 2026. New records show when each source confirmed them.

Sources

References from the CNA

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.