# October CMS incomplete URL scheme validation in image resizer

Source: https://junglewise.ai/threats/october-cms-incomplete-url-scheme-validation-in-image-resizer-f7555212  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-14. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: low · CVSS 3.9 · Published 2026-09-14

October CMS's image resizer feature allows templates to resize and cache remote images. A weakness in URL validation allows non-HTTP schemes (like phar://, file://, ftp://) to be stored in the cache and later passed to the underlying image library. If a template author passes untrusted input to the resize filter without validation, an attacker could exploit PHP deserialization via phar:// URLs, potentially achieving code execution. This risk is limited to installations where templates accept and process user-supplied URLs.

Technologies: [october/october (Packagist)](https://junglewise.ai/threats/technologies/october-october). Vendors: [Packagist](https://junglewise.ai/threats/vendors/packagist).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Low severity, with a CVSS score of 3.9, published 14 September 2026.

**Which products and versions are affected?** october/october (Packagist) >= 4.3.0, < 4.3.4.

**Is there a fix for This vulnerability?** A patch was published on 2026-09-14: Patch released in version 4.3.5 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a web application.

**Am I affected?** Check whether you run october/october (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an improper input validation weakness (CWE-20) in the ResizeImageItem::fromObject() method. The resizer classified external sources by checking if the string began with "http" and accepted any value containing "://" as a valid URL. This allows non-HTTP(S) PHP stream wrappers (phar://, file://, ftp://) to bypass scheme validation, be stored in the resizer cache, and later passed to the underlying image library. On phar:// paths, this can trigger metadata deserialization during file operations, potentially leading to RCE. Exploitation requires a pre-existing injection primitive—specifically, template-authoring or backend-configuration code that pipes untrusted input into the |resize Twig filter or ResizeImages::resize() API without validation. The public /resize/{file} route is a cache lookup and cannot be exploited directly by an unauthenticated user. The issue is fixed in version 4.3.5.

## Affected products

- October CMS October >= 4.3.0, < 4.3.4

## Timeline

- 2026-09-14: disclosed: October CMS Incomplete Scheme Validation vulnerability disclosed via GHSA-2xmm-m4wv-3fjh
- 2026-09-14: patched: Patch released in version 4.3.5

## References

- [https://api.github.com/users/0xGenesi](https://api.github.com/users/0xGenesi)
- [https://github.com/0xGenesi](https://github.com/0xGenesi)
- [https://api.github.com/users/0xGenesi/gists%7B/gist_id%7D](https://api.github.com/users/0xGenesi/gists%7B/gist_id%7D)
- [https://api.github.com/users/0xGenesi/repos](https://api.github.com/users/0xGenesi/repos)
- [https://avatars.githubusercontent.com/u/294995388?v=4](https://avatars.githubusercontent.com/u/294995388?v=4)
- [https://api.github.com/users/0xGenesi/events%7B/privacy%7D](https://api.github.com/users/0xGenesi/events%7B/privacy%7D)

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- [October allows an admin account to upload PDF containing malicious JavaScript](https://junglewise.ai/threats/cve-2024-45962-october-allows-an-admin-account-to-upload-pdf-containing)
- [October CMS Cross-site Scripting vulnerability](https://junglewise.ai/threats/cve-2023-25365-october-cms-cross-site-scripting-vulnerability)
- [Stored Cross-Site Scripting October CMS](https://junglewise.ai/threats/cve-2023-37692-stored-cross-site-scripting-october-cms)