CVE-2026-33691
Last modified
CVE-2026-33691 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 3.58% chance of exploitation in the next 30 days.
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Owasp | Owasp Modsecurity Core Rule Set | < 3.3.9 |
| Owasp | Owasp Modsecurity Core Rule Set | >= 4.0.0, < 4.25.0 |
References
- https://github.com/coreruleset/coreruleset/pull/4546Issue Tracking, Patch
- https://github.com/coreruleset/coreruleset/pull/4547Issue Tracking, Patch
- https://github.com/coreruleset/coreruleset/releases/tag/v3.3.9Product, Release Notes
- https://github.com/coreruleset/coreruleset/releases/tag/v4.25.0Product, Release Notes
- https://github.com/coreruleset/coreruleset/security/advisories/GHSA-rw5f-9w43-gv2wMitigation, Patch, Vendor Advisory
- http://seclists.org/fulldisclosure/2026/Apr/0Mailing List, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2026/03/29/2Mailing List, Third Party Advisory
Timeline
- Published
- Last Modified
- Status
- Modified
Frequently Asked Questions
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How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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