CVE-2026-33691
Medium
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.
SeverityMedium
CVSS6.8
Exploit probability—
ProductOwasp Modsecurity Core Rule Set
PublishedApr 2, 2026
First seenApr 2, 2026
Weakness typeCWE-178CWE-178
How to fix
Update
- owasp owasp_modsecurity_core_rule_set3.3.9, 4.25.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| owasp owasp_modsecurity_core_rule_set | v < 3.3.9, 4.0.0 ≤ v < 4.25.0 | 3.3.9, 4.25.0 |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.