CVE-2026-52761 in ModSecurity
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 through 3.0.15, the t:utf8toUnicode transformation in src/actions/transformations/utf8_to_unicode.cc produces wrong output on i386...
Quick answer
OWASP ModSecurity should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- ModSecurity >=3.0.0 <3.0.16
Fixed versions
- ModSecurity 3.0.16 or later
How to fix it
Update ModSecurity. The old WAF build can miss input that a rule should catch on some systems.
- Upgrade ModSecurity to ModSecurity 3.0.16 or later.
- Restart the web server or WAF service.
- Reload the rule set.
- Watch logs for blocked and allowed requests.
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Verify the fix
- Confirm ModSecurity reports the fixed version.
- Scan again and confirm CVE-2026-52761 is gone.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-52761?
OWASP ModSecurity versions listed as affected should be reviewed: ModSecurity >=3.0.0 <3.0.16.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.