CVE-2026-55676 Malcolm vulnerable to RCE via unrestricted .php upload to the file-upload component
An attacker with upload privileges can execute arbitrary PHP code by uploading a malicious file due to missing file type restrictions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-55676?
CVE-2026-55676 is a high-severity vulnerability in cisagov Malcolm, published on 11 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Malcolm is a network traffic analysis tool suite. The file-upload component (FilePond PHP backend) accepts uploads at `POST /server/php/submit.php` and stores them in a directory served by the same nginx and php-fpm instance. The allow-list that should restrict accepted file types is an empty array by default (`file-upload/php/config.php:16`), so the type check is a no-op and every extension is accepted. The filename sanitizer keeps the `.php` extension intact. Committed files land in `/var/www/upload/server/php/files` (`file-upload/php/config.php:7`), and the component's nginx routes any URL ending in `.php` to php-fpm. An authenticated `GET /server/php/files/<name>.php` then executes the uploaded code as `www-data`. Prior to version 26.06.1, in RBAC mode, the upload endpoint is reachable by the granular `ROLE_UPLOAD` role (`nginx/lua/nginx_auth_helpers.lua:71`), a role intended only for submitting capture files. As a result, a user holding the upload-only role runs arbitrary PHP as `www-data` inside the file-upload container. Version 26.06.1 fixes the issue.
Weakness: CWE-434
Which versions are affected by CVE-2026-55676?
How do I fix CVE-2026-55676?
No fix has been published for CVE-2026-55676 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-55676 being exploited?
There is no known exploitation of CVE-2026-55676 in the wild and no public exploit code.
Sources
Also known as GHSA-8cvp-m7pg-qrp7.