CVE-2026-21876
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.
Scoring
- Severity
- CRITICAL
- CVSS base score
- 9.3
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
- EPSS probability
- 14.22%
- CWE
- CWE-794
- Published
- 2026-01-08
- Last modified
- 2026-04-10
Affected products
- coreruleset coreruleset
- coreruleset coreruleset
Weakness type
Related vulnerabilities
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- CVE-2021-0203 — Junos OS: EX and QFX5K Series: Storm Control does not work as expected when Redundant Trunk Group is configured
- CVE-2020-1665 — Junos OS: MX series/EX9200 Series: IPv6 DDoS protection does not work as expected.
- CVE-2019-0002 — Junos OS: EX2300 and EX3400 series: Certain stateless firewall filter rules might not take effect