CVE-2026-33691
MEDIUMEPSS 88th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
Exploit Intelligence
Elevated risk: more likely to be exploited than 88% of all known CVEs.
References
Related Vulnerabilities
Other CWE-178 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-27636 | Medium | 5.6 | 81% | - | Fix |
| CVE-2021-24347 | High | 8.8 | 54% | - | Fix |
| CVE-2020-12812 | Critical | 9.8 | 49% | KEV + Ransom | Fix |
| CVE-2003-0411 | High | 7.5 | 25% | - | - |
| CVE-2018-9845 | Critical | 9.8 | 13% | - | Fix |
| CVE-2001-0766 | Critical | 9.8 | 8.2% | - | - |
Common questions
How do I fix CVE-2026-33691?
Upgrade modsecurity-crs on debian 12 to 3.3.4-1+deb12u3 or later.
Is CVE-2026-33691 being actively exploited?
Not that we know of. CVE-2026-33691 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 3.6% is the estimated probability that it will be exploited in the next 30 days. That is higher than 88% of all scored CVEs.
How severe is CVE-2026-33691?
CVE-2026-33691 has a CVSS v3 base score of 6.8, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-33691 affect?
Published advisories record a fix for modsecurity-crs (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-33691
Markdown
[](https://tridentstack.com/cve/CVE-2026-33691)HTML
<a href="https://tridentstack.com/cve/CVE-2026-33691"><img src="https://tridentstack.com/cve/badge/CVE-2026-33691.svg" alt="CVE-2026-33691"></a>Find and fix vulnerabilities across your fleet
TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-24.