CVE-2026-21876 is a critical severity vulnerability with a CVSS score of 9.3. Exploits are available; patches have been released and should be applied urgently.
Very low probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
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.
Please cite this page when referencing data from Strobes VI. Proper attribution helps support our vulnerability intelligence research.