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CVE-2026-33691 (GCVE-0-2026-33691)

Vulnerability from cvelistv5 – Published: 2026-04-02 15:03 – Updated: 2026-04-18 19:16

Title

OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks

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 3.3.9 and 4.25.0, a bypass was identified in OWASP CRS that allows uploading files with dangerous extensions (.php, .phar, .jsp, .jspx) by inserting whitespace padding in the filename (e.g. photo. php or shell.jsp ). The affected rules do not normalize whitespace before evaluating the file extension regex, so the dot-extension check fails to match. This issue has been patched in versions 3.3.9 and 4.25.0.

Severity

6.8 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-178 - Improper Handling of Case Sensitivity

Assigner

GitHub_M

References

10 references

URL	Tags
https://github.com/coreruleset/coreruleset/securi…	x_refsource_CONFIRM
https://github.com/coreruleset/coreruleset/pull/4546	x_refsource_MISC
https://github.com/coreruleset/coreruleset/pull/4547	x_refsource_MISC
https://github.com/coreruleset/coreruleset/pull/4548	x_refsource_MISC
https://github.com/coreruleset/coreruleset/commit…	x_refsource_MISC
https://github.com/coreruleset/coreruleset/releas…	x_refsource_MISC
https://github.com/coreruleset/coreruleset/releas…	x_refsource_MISC
http://www.openwall.com/lists/oss-security/2026/03/29/2
http://seclists.org/fulldisclosure/2026/Apr/0
http://www.openwall.com/lists/oss-security/2026/04/18/4

Impacted products

1 product

Vendor	Product	Version
coreruleset	coreruleset	Affected: < 3.3.9 Affected: >= 4.0.0-rc1, < 4.25.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-04-18T19:16:54.006Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
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        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/03/29/2"
          },
          {
            "url": "http://seclists.org/fulldisclosure/2026/Apr/0"
          },
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/04/18/4"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-33691",
                "options": [
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                    "Exploitation": "none"
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                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
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                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-02T17:38:01.007742Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-02T17:38:10.247Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "coreruleset",
          "vendor": "coreruleset",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.3.9"
            },
            {
              "status": "affected",
              "version": "\u003e= 4.0.0-rc1, \u003c 4.25.0"
            }
          ]
        }
      ],
      "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 3.3.9 and 4.25.0, a bypass was identified in OWASP CRS that allows uploading files with dangerous extensions (.php, .phar, .jsp, .jspx) by inserting whitespace padding in the filename (e.g. photo. php or shell.jsp ). The affected rules do not normalize whitespace before evaluating the file extension regex, so the dot-extension check fails to match. This issue has been patched in versions 3.3.9 and 4.25.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N",
            "version": "3.1"
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          "url": "https://github.com/coreruleset/coreruleset/pull/4547"
        },
        {
          "name": "https://github.com/coreruleset/coreruleset/pull/4548",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/coreruleset/coreruleset/pull/4548"
        },
        {
          "name": "https://github.com/coreruleset/coreruleset/commit/2a8c63512811c5dd74472becebb79a783e68ff02",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/coreruleset/coreruleset/commit/2a8c63512811c5dd74472becebb79a783e68ff02"
        },
        {
          "name": "https://github.com/coreruleset/coreruleset/releases/tag/v3.3.9",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/coreruleset/coreruleset/releases/tag/v3.3.9"
        },
        {
          "name": "https://github.com/coreruleset/coreruleset/releases/tag/v4.25.0",
          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/coreruleset/coreruleset/releases/tag/v4.25.0"
        }
      ],
      "source": {
        "advisory": "GHSA-rw5f-9w43-gv2w",
        "discovery": "UNKNOWN"
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      "title": "OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33691",
    "datePublished": "2026-04-02T15:03:52.126Z",
    "dateReserved": "2026-03-23T16:34:59.932Z",
    "dateUpdated": "2026-04-18T19:16:54.006Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

CVE-2026-21876 (GCVE-0-2026-21876)

Vulnerability from cvelistv5 – Published: 2026-01-08 13:55 – Updated: 2026-04-09 15:41

Title

OWASP CRS has multipart bypass using multiple content-type parts

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.

Severity

9.3 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-794 - Incomplete Filtering of Multiple Instances of Special Elements

Assigner

GitHub_M

References

6 references

URL	Tags
https://github.com/coreruleset/coreruleset/securi…	x_refsource_CONFIRM
https://github.com/coreruleset/coreruleset/commit…	x_refsource_MISC
https://github.com/coreruleset/coreruleset/commit…	x_refsource_MISC
https://github.com/coreruleset/coreruleset/releas…	x_refsource_MISC
https://github.com/coreruleset/coreruleset/releas…	x_refsource_MISC
https://github.com/daytriftnewgen/CVE-2026-21876	exploit

Impacted products

1 product

Vendor	Product	Version
coreruleset	coreruleset	Affected: < 4.22.0 Affected: < 3.3.8

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-21876",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
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                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-01-08T14:52:48.615550Z",
                "version": "2.0.3"
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              "type": "ssvc"
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        "providerMetadata": {
          "dateUpdated": "2026-04-09T15:41:17.073Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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            "tags": [
              "exploit"
            ],
            "url": "https://github.com/daytriftnewgen/CVE-2026-21876"
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        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "coreruleset",
          "vendor": "coreruleset",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.22.0"
            },
            {
              "status": "affected",
              "version": "\u003c 3.3.8"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 9.3,
            "baseSeverity": "CRITICAL",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
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            "version": "3.1"
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      "providerMetadata": {
        "dateUpdated": "2026-01-08T13:55:37.102Z",
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      "references": [
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          "name": "https://github.com/coreruleset/coreruleset/security/advisories/GHSA-36fv-25j3-r2c5",
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          "tags": [
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          "url": "https://github.com/coreruleset/coreruleset/releases/tag/v3.3.8"
        },
        {
          "name": "https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0",
          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/coreruleset/coreruleset/releases/tag/v4.22.0"
        }
      ],
      "source": {
        "advisory": "GHSA-36fv-25j3-r2c5",
        "discovery": "UNKNOWN"
      },
      "title": "OWASP CRS has multipart bypass using multiple content-type parts"
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  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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Find a vulnerability

Search criteria ⓘ Use this form to refine search results.
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2 vulnerabilities by coreruleset

CVE-2026-33691 (GCVE-0-2026-33691)

CVE-2026-21876 (GCVE-0-2026-21876)

Find a vulnerability

Search criteria ⓘ Use this form to refine search results. Full-text search supports keyword queries with ranking and filtering. You can combine vendor, product, and sources to narrow results. Enable “Apply ordering” to sort by date instead of relevance.

2 vulnerabilities by coreruleset

CVE-2026-33691 (GCVE-0-2026-33691)

CVE-2026-21876 (GCVE-0-2026-21876)

Search criteria ⓘ Use this form to refine search results.
Full-text search supports keyword queries with ranking and filtering.
You can combine vendor, product, and sources to narrow results.
Enable “Apply ordering” to sort by date instead of relevance.