---
id: CVE-2026-52747
title: >-
  ModSecurity is an open source, cross platform web application firewall (WAF)
  engine for Apache, IIS and Nginx
summary: >-
  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-…
severity: high
cvss: 8.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N'
cwe:
  - CWE-180
published: '2026-07-10'
updated: '2026-07-10'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52747'
references:
  - url: >-
      https://github.com/owasp-modsecurity/ModSecurity/commit/875504c2758169c41be1ad2f0cc64d896b7815d7
    label: security-advisories@github.com
  - url: 'https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.16'
    label: security-advisories@github.com
  - url: >-
      https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-rcw9-2f5r-7p88
    label: security-advisories@github.com
tags:
  - nvd
epss: 0.00476
epssPercentile: 0.38502
ingestedAt: '2026-07-11T22:16:00.520Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.