CVE-2026-21876 (GCVE-0-2026-21876)

Vulnerability from cvelistv5 – Published: 2026-01-08 13:55 – Updated: 2026-01-08 15:55
VLAI?
Title
OWASP CRS has multipart bypass using multiple content-type parts
Summary
The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls. Prior to versions 4.22.0 and 3.3.8, the current rule 922110 has a bug when processing multipart requests with multiple parts. When the first rule in a chain iterates over a collection (like `MULTIPART_PART_HEADERS`), the capture variables (`TX:0`, `TX:1`) get overwritten with each iteration. Only the last captured value is available to the chained rule, which means malicious charsets in earlier parts can be missed if a later part has a legitimate charset. Versions 4.22.0 and 3.3.8 patch the issue.
Severity ?
9.3 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
CWE
  • CWE-794 - Incomplete Filtering of Multiple Instances of Special Elements
Assigner
References
Impacted products
Vendor Product Version
coreruleset coreruleset Affected: < 4.22.0
Affected: < 3.3.8
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  • 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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.