Input validation error in October CMS - CVE-2026-100909
Published: September 14, 2026 / Updated: September 28, 2026
Vulnerability identifier: #VU149489
CSH Severity: Low
CVSS v4: 1.8 [CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:A/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-100909
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to trigger metadata deserialization.
The vulnerability exists due to improper scheme validation in the image resizer's ResizeImageItem::fromObject() string-source handling when processing untrusted string input passed to the |resize Twig filter or ResizeImages::resize() API. A remote privileged user can provide a phar:// source through untrusted input to trigger metadata deserialization.
Metadata deserialization can occur during subsequent file operations.
Affected software
October CMS
How to mitigate CVE-2026-100909
Install security update from vendor's website.
October CMS - update to 4.3.5