Deserialization of Untrusted Data in October CMS - CVE-2026-49400
Published: September 14, 2026
Vulnerability identifier: #VU149492
CSH Severity: Low
CVSS v4: 2.1 [CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-49400
CWE-ID: CWE-502
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to execute arbitrary PHP code.
The vulnerability exists due to deserialization of untrusted data in the backend SessionMaker trait when reading widget session state. A remote privileged user can write attacker-controlled data to a widget session key to execute arbitrary PHP code.
Exploitation requires cms.safe_mode to be enabled and a suitable PHP gadget chain reachable from the installed dependency set.
Affected software
October CMS
How to mitigate CVE-2026-49400
Install security update from vendor's website.
October CMS - addressed in versions 3.7.17, 4.2.21