🛡️ CVE-2026-52747 on Debian — modsecurity

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-52747 as tracked by Debian, for the package modsecurity. The fix is available in version 3.0.16-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality none, integrity high, availability none.

Weakness class

DEBIAN-CVE-2026-52747 is classified as CWE-180: Incorrect Behavior Order: Validate Before Canonicalize. The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.

Affected software

DEBIAN-CVE-2026-52747 is recorded against 1 package.

modsecurity (fixed in 3.0.16-1)

Timeline and source

Published on 10 July 2026 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

Details

Severity Unknown

CVSS Score N/A

CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2026-07-10

Updated 2026-08-20

Modified 2026-08-04

Fix URL N/A

Affected Packages

Software	From version	Fixed in
modsecurity	—	3.0.16-1

References

ADVISORY https://security-tracker.debian.org/tracker/CVE-2026-52747

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