CVE-2026-52747: owasp-modsecurity modsecurity

Vulnerability summary

CVE-2026-52747 is a high (CVSS 8.6) vulnerability in owasp-modsecurity modsecurity. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 39.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 10-07-2026
   PublishedVulnerability first disclosed.
2. 13-07-2026
   Last modifiedVulnerability information updated.

Description

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 3.0.16, the multipart/form-data request body parser in libmodsecurity silently removes embedded line breaks from non-file form-field values before exporting them to ARGS and ARGS_POST because src/request_body_processor/multipart.cc overwrites reserved bytes in m_reserve instead of appending the current buffer. This creates a parser differential between ModSecurity and backend applications that preserve line breaks in form fields, allowing rules that inspect ARGS or ARGS_POST to miss payloads whose dangerous syntax depends on a line break. This issue is fixed in version 3.0.16.

• CWE-180Incorrect Behavior Order: Validate Before CanonicalizeThe product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.