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VulnerabilityPublished

CVE-2025-52891: ModSecurity · Improper Input Validation

Affects ModSecuritySource CVE Database V5

0

Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.9.11 when convenient.

Data as of 26 Oct 2026, 11:42 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 31% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.9.11
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Jul 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade owasp-modsecurity/ModSecurity to 2.9.11.

Affected software

ProductAffectedFixed in
GitHubowasp-modsecurity/ModSecuritypkg:github/owasp-modsecurity/ModSecurityOther threatsAffected
  • <2.9.11 >=2.9.8
Fixed in
  • 2.9.11

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should prioritize upgrading ModSecurity to version 2.9.11 or later, where this vulnerability is patched. Until the upgrade can be performed, a practical workaround is to disable XML argument parsing by setting SecParseXmlIntoArgs to 'Off' in the ModSecurity configuration, which prevents the segmentation fault from occurring. Additionally, organizations should review their WAF configurations to minimize exposure to XML-based inputs where possible, and implement strict input validation and filtering at the application level. Monitoring ModSecurity logs for crashes or unusual restarts can help detect exploitation attempts. Network-level protections such as rate limiting and IP reputation filtering can reduce the likelihood of repeated attack attempts. Finally, organizations should ensure robust incident response plans are in place to quickly restore WAF functionality and investigate potential follow-on attacks during any downtime.

Description

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. In versions 2.9.8 to before 2.9.11, an empty XML tag can cause a segmentation fault. If SecParseXmlIntoArgs is set to On or OnlyArgs, and the request type is application/xml, and at least one XML tag is empty (eg <foo></foo>), then a segmentation fault occurs. This issue has been patched in version 2.9.11. A workaround involves setting SecParseXmlIntoArgs to Off.

References

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