Incorrect Behavior Order: Validate Before Canonicalize in ModSecurity - CVE-2026-52747
Published: June 29, 2026
Vulnerability identifier: #VU135853
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-52747
CWE-ID: CWE-180
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Trustwave
Affected software:
ModSecurity
ModSecurity
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass request-body inspection.
The vulnerability exists due to incorrect behavior order: validate before canonicalize in the libmodsecurity multipart/form-data request body parser when processing non-file multipart form-field values containing embedded line breaks. A remote attacker can send a specially crafted multipart/form-data request to bypass request-body inspection.
The issue affects values exported to ARGS and ARGS_POST, while built-in multipart strict-validation variables can remain clear.
How to mitigate CVE-2026-52747
Install security update from vendor's website.