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Vulnerabilities

Security fix · CVE-2026-21876

The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls.

Published Jan 8, 2026 · catalog updated Apr 9, 2026 · The OWASP core rule

Last checked Oct 30, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2026-21876 is not in CISA KEV. FIRST estimates a 17.88% chance of exploitation in the next 30 days. Check whether you run The OWASP core rule.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (The OWASP core rule).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
17.88%
Remediation
Version ranges on file
Affected products
vendor coreruleset coreruleset < 3.3.8

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 ), the capture variables ( , ) 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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor coreruleset coreruleset < 3.3.8< 3.3.8

How to fix CVE-2026-21876

  • Upgrade

    CVE-2026-21876 lists a fix boundary at 3.3.8. Compare the installed build with that boundary before you change production.

  • Version check

    Affected < 3.3.8

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2026-21876 is not in CISA KEV. FIRST estimates a 17.88% chance of exploitation in the next 30 days. Check whether you run The OWASP core rule.

Which versions are affected?

Compare what you have installed with coreruleset coreruleset < 3.3.8 < 3.3.8. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 17.88%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Jan 8, 2026 · EUVD

    Detected

    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 ), the capture variables ( , ) get overwritten with each iteration. Only the last capt

  2. Apr 9, 2026 · EUVD

    Updated

    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 ), the capture variables ( , ) get overwritten with each iteration. Only the last capt

Sources

  • EUVDVulnerability recordEUVD-2026-1669

    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

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Apr 9, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • EUVDOct 30, 2026