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.
Published: 2026-04-02
Score: 6.8 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Unrestricted file upload leading to potential code execution
Action: Immediate Patch
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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History

Sat, 18 Apr 2026 20:30:00 +0000

Type Values Removed Values Added
References

Tue, 07 Apr 2026 15:15:00 +0000

Type Values Removed Values Added
First Time appeared Owasp
Owasp owasp Modsecurity Core Rule Set
CPEs cpe:2.3:a:owasp:owasp_modsecurity_core_rule_set:*:*:*:*:*:*:*:*
Vendors & Products Owasp
Owasp owasp Modsecurity Core Rule Set

Fri, 03 Apr 2026 06:30:00 +0000

Type Values Removed Values Added
References

Thu, 02 Apr 2026 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Coreruleset
Coreruleset coreruleset
Vendors & Products Coreruleset
Coreruleset coreruleset
References
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 02 Apr 2026 15:45:00 +0000

Type Values Removed Values Added
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.
Title OWASP CRS: Whitespace padding in filenames bypasses file upload extension checks
Weaknesses CWE-178
References
Metrics cvssV3_1

{'score': 6.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N'}


Subscriptions

Coreruleset Coreruleset
Owasp Owasp Modsecurity Core Rule Set
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-18T19:16:54.006Z

Reserved: 2026-03-23T16:34:59.932Z

Link: CVE-2026-33691

cve-icon Vulnrichment

Updated: 2026-04-18T19:16:54.006Z

cve-icon NVD

Status : Modified

Published: 2026-04-02T16:16:22.593

Modified: 2026-04-18T20:16:29.633

Link: CVE-2026-33691

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-04-08T19:55:39Z

Weaknesses