FKIE_CVE-2026-21876

Vulnerability from fkie_nvd - Published: 2026-01-08 14:15 - Updated: 2026-01-08 18:08
Severity ?
9.3 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Summary
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.
References
security-advisories@github.comhttps://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83
security-advisories@github.comhttps://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6
security-advisories@github.comhttps://github.com/coreruleset/coreruleset/releases/tag/v3.3.8
security-advisories@github.comhttps://github.com/coreruleset/coreruleset/releases/tag/v4.22.0
security-advisories@github.comhttps://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5
Impacted products
Vendor Product Version
To clipboard 

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "id": "CVE-2026-21876",
  "lastModified": "2026-01-08T18:08:18.457",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.3,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-08T14:15:57.087",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/coreruleset/coreruleset/commit/80d80473abf71bd49bf6d3c1ab221e3c74e4eb83"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/coreruleset/coreruleset/commit/9917985de09a6cf38b3261faf9105e909d67a7d6"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/coreruleset/coreruleset/releases/tag/v3.3.8"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-794"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


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Detection rules are retrieved from Rulezet.