Access of Uninitialized Pointer in ModSecurity - CVE-2026-73857
Published: November 4, 2026
Vulnerability identifier: #VU159008
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-73857
CWE-ID: CWE-824
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to access of an uninitialized pointer in the ModSecurity v3 XML request body processor when processing XML request bodies in the XML-into-ARGS SAX end-element callback. A remote attacker can send a single crafted HTTP request to trigger dereferencing of XMLNodes::parsing_ctx_arg, causing a constant value to be written to an attacker-controlled address and crashing the web server worker process.
The vulnerable code path is reachable only when SecParseXmlIntoArgs is set to On or OnlyArgs; the directive is Off by default.
Affected software
ModSecurity
How to mitigate CVE-2026-73857
Install security update from vendor's website.
ModSecurity - update to 3.0.17