# CVE-2026-33691: modsecurity-crs: The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application fire...

CVE-2026-33691 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-33691, released April 2, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-33691
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0385
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 2, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | mod_security_crs amzn 2023 | 4.2.0-1.amzn2023.0.3 | [ALAS2023-2026-1562](https://patchblox.com/security/data/fix/linux/alas2023-2026-1562.md) | Apr 13, 2026 |
| Linux | modsecurity-crs Debian 12.15 (bookworm) | 3.3.4-1+deb12u3 | [DEBIAN-CVE-2026-33691](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33691.md) | Apr 2, 2026 |
| Linux | modsecurity-crs Debian 13.5 (trixie) | 3.3.7-1+deb13u2 | [DEBIAN-CVE-2026-33691](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33691.md) | Apr 2, 2026 |
| Linux | modsecurity-crs Debian 14 | 3.3.9-1 | [DEBIAN-CVE-2026-33691](https://patchblox.com/security/data/fix/linux/debian-cve-2026-33691.md) | Apr 2, 2026 |

---

Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.