CVE-2026-21876
9.3 · CRITICALOverview
CVE-2026-21876 is a critical-severity vulnerability affecting owasp owasp_modsecurity_core_rule_set. It was published on January 8, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
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.
Remediation
Check the references section for vendor advisories and patches from owasp. Update owasp_modsecurity_core_rule_set to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| owasp | owasp_modsecurity_core_rule_set | >= 0, < 3.3.8 | Affected |
References
Frequently Asked Questions
What is CVE-2026-21876?
CVE-2026-21876 is a critical-severity vulnerability affecting owasp owasp_modsecurity_core_rule_set. It was published on January 8, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).
How severe is CVE-2026-21876?
This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-21876?
Check the references section for vendor advisories and patches from owasp. Update owasp_modsecurity_core_rule_set to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-21876?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-21876 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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