{
    "id": "CVE-2026-21876",
    "published": "2026-01-08 14:15:57",
    "last_modified": "2026-06-17 10:19:04",
    "cvss_score": "9.3",
    "cvss_severity": "CRITICAL",
    "cvss_version": "3.1",
    "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N",
    "cwe": "CWE-794",
    "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.",
    "epss_score": "0.17507",
    "epss_percentile": "0.97038",
    "kev": 0,
    "kev_due": null,
    "has_exploit": 1,
    "updated_at": "2026-09-27 18:17:55",
    "priority": {
        "rank": 2,
        "label": "Patch early",
        "why": "A public exploit exists."
    },
    "products": [
        {
            "vendor": "owasp",
            "product": "owasp_modsecurity_core_rule_set"
        }
    ],
    "kev_detail": null,
    "exploits": [
        {
            "source": "exploit-db",
            "ref_id": "52558",
            "title": "coreruleset 4.21.0 - Firewall Bypass",
            "date": "2026-05-13",
            "url": "https://www.exploit-db.com/exploits/52558"
        }
    ],
    "refs_list": [
        "https://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83",
        "https://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6",
        "https://github.com/coreruleset/coreruleset/releases/tag/v3.3.8",
        "https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0",
        "https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5",
        "https://github.com/daytriftnewgen/CVE-2026-21876"
    ]
}