CVE-2026-100909 OctoberCMS ResizeImages.php getSourcePathForResize server-side request forgery
Remote attackers can exploit a server-side request forgery vulnerability in OctoberCMS to access internal resources or bypass security controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-100909?
CVE-2026-100909 is a medium-severity server-side request forgery vulnerability in OctoberCMS, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A vulnerability was found in OctoberCMS up to 4.1.19/4.2.25/4.3.4. The impacted element is the function getSourcePathForResize of the file modules/system/classes/ResizeImages.php. The manipulation of the argument realSourcePath results in server-side request forgery. The attack may be performed from remote. The exploit has been made public and could be used. Upgrading to version 4.3.5 and 4.4.0 is sufficient to resolve this issue. The patch is identified as 0e9736aa2c6d6bd3d60ff6ef9e0b4d32ce387f58. The affected component should be upgraded.
Weakness: CWE-918
Which versions are affected by CVE-2026-100909?
2 open source packages ship an affected version, including october/october.
| Package | Affected | Fixed in |
|---|---|---|
october/october Packagist | From 4.3.0 | 4.3.5 |
october/october Packagist | From 4.3.0 | 4.3.5 |
How do I fix CVE-2026-100909?
Upgrade october/october to 4.3.5 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-100909 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100909 exists.
Sources
Also known as GHSA-2xmm-m4wv-3fjh, GHSA-5528-3vrx-6443.