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Vulnerability record · CVE-2026-33691 · published 2 April 2026

CVE-2026-33691: Owasp modsecurity core rule set vulnerability

Owasp · Owasp Modsecurity Core Rule Set

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.

7.5 CVSS 3.1 High EPSS 1.6% · top 25.5% CWE-178 · CWE-178
7.5CVSS 3.1 base score
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References
24 Jul 2026Last modified by NVD

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 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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/coreruleset/coreruleset/commit/2a8c63512811c5dd74472becebb79a783e68ff02 Patch
https://github.com/coreruleset/coreruleset/pull/4546 Issue TrackingPatch
https://github.com/coreruleset/coreruleset/pull/4547 Issue TrackingPatch
https://github.com/coreruleset/coreruleset/pull/4548 Patch
https://github.com/coreruleset/coreruleset/releases/tag/v3.3.9 ProductRelease Notes
https://github.com/coreruleset/coreruleset/releases/tag/v4.25.0 ProductRelease Notes
https://github.com/coreruleset/coreruleset/security/advisories/GHSA-rw5f-9w43-gv2w MitigationPatchVendor Advisory
http://seclists.org/fulldisclosure/2026/Apr/0 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/03/29/2 Mailing ListThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/04/18/4

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2022-39955Owasp modsecurity core rule set incorrect authorization vulnerabilityThe OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass by submitting a specially crafted HTTP Content-Type header field t…EPSS 1.4%9.8CVE-2022-39956Owasp modsecurity core rule set incorrect authorization vulnerabilityThe OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a ch…EPSS 1.2%9.8CVE-2020-22669Owasp modsecurity core rule set sql injection vulnerabilityModsecurity owasp-modsecurity-crs 3.2.0 (Paranoia level at PL1) has a SQL injection bypass vulnerability. Attackers can use the comment characters an…EPSS 1.3%9.8CVE-2021-35368Owasp modsecurity core rule set vulnerabilityOWASP ModSecurity Core Rule Set 3.1.x before 3.1.2, 3.2.x before 3.2.1, and 3.3.x before 3.3.2 is affected by a Request Body Bypass via a trailing pa…EPSS 2.7%7.5CVE-2022-39957Owasp modsecurity core rule set vulnerabilityThe OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass. A client can issue an HTTP Accept header field containing an optiona…EPSS 0.99%7.5CVE-2022-39958Owasp modsecurity core rule set incorrect authorization vulnerabilityThe OWASP ModSecurity Core Rule Set (CRS) is affected by a response body bypass to sequentially exfiltrate small and undetectable sections of data by…EPSS 1.2%7.5CVE-2018-16384Owasp modsecurity core rule set sql injection vulnerabilityA SQL injection bypass (aka PL1 bypass) exists in OWASP ModSecurity Core Rule Set (owasp-modsecurity-crs) through v3.1.0-rc3 via {`a`b} where a is a …EPSS 1.7%5.3CVE-2026-21876Owasp modsecurity core rule set vulnerabilityThe 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 …EPSS 18%

Source: NIST National Vulnerability Database (record CVE-2026-33691), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.