OWASP CRS has multipart bypass using multiple content-type parts_CVE-2026-21876

{
    "lastseen": "",
    "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.",
    "published": "2026-01-08T13:55:37.102Z",
    "modified": "2026-01-08T13:55:37.102Z",
    "type": "cve",
    "title": "OWASP CRS has multipart bypass using multiple content-type parts",
    "source": "GitHub_M",
    "references": "https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5\nhttps://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83\nhttps://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6\nhttps://github.com/coreruleset/coreruleset/releases/tag/v3.3.8\nhttps://github.com/coreruleset/coreruleset/releases/tag/v4.22.0",
    "id": "CVE-2026-21876",
    "bulletinFamily": "",
    "cwe": [
        "CWE-794"
    ],
    "cvelist": null,
    "sourceData": "coreruleset coreruleset < 4.22.0\ncoreruleset coreruleset < 3.3.8",
    "sourceHref": "",
    "cvss": {
        "score": 9.3,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "coreruleset",
    "version": "< 4.22.0",
    "vendor": "coreruleset",
    "ai_description": "Multipart bypass vulnerability in OWASP CRS using multiple content-type parts",
    "ai_severity": "Critical",
    "ai_vendor": "OWASP",
    "ai_product": "OWASP Core Rule Set (CRS)",
    "ai_version": "< 4.22.0, < 3.3.8",
    "ai_score": 9.3
}