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Vulnerabilities

Vulnerability · CVE-2026-33691

The OWASP core rule set (CRS) is a set of generic attack detection rules for use with compatible web application firewalls.

Published Apr 2, 2026 · catalog updated Jul 24, 2026 · owasp modsecurity core rule set

Check if you run it

No confirmed exploitation is on record for CVE-2026-33691. EPSS is 1.58%. Act only if a listed version of owasp modsecurity core rule set is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.58%
Remediation
Version ranges on file
Affected products
cpe owasp/owasp modsecurity core rule set

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe owasp/owasp modsecurity core rule set< 3.3.9
  • cpe owasp/owasp modsecurity core rule set< 4.25.0

How to fix CVE-2026-33691

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-33691. EPSS is 1.58%. Act only if a listed version of owasp modsecurity core rule set is installed.

Which versions are affected?

Compare what you have installed with owasp/owasp modsecurity core rule set < 3.3.9; owasp/owasp modsecurity core rule set < 4.25.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-178. EPSS 1.58%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 2, 2026 · NIST NVD

    Detected

    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 white

  2. Jul 24, 2026 · NIST NVD

    Updated

    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 white

Sources

  • CVE.orgVulnerability recordCVE-2026-33691

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-33691

    30-day exploitation probability 1.6%

    first.org
  • NIST NVDVulnerability recordCVE-2026-33691

    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

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.