critical CVSS 9.8

CVE-2025-21624·PHP vulnerability

ClipBucket V5 provides open source video hosting with PHP. Prior to 5.5.1 - 239, a file upload vulnerability exists in the Manage Playlist functionality of the application, specifically surrounding the uploading of playlist cover images. Without proper checks, an attacker can upload a PHP script file instead of an image file, thus allowing a webshell or other malicious files to be stored and executed on the server. This attack vector exists in both the admin area and low-level user area. This vulnerability is fixed in 5.5.1 - 239.

Severity
critical
Software
PHP
Fixed in
5.5.1-239
Published
2025-01-07

Affected versions

From: 5.3

Until: 5.5.1-239

Fixed in: 5.5.1-239

How to fix this CVE

ClipBucket versions 5.3 through 5.5.1-238 contain a critical file upload vulnerability in the playlist cover image feature that allows unauthenticated attackers to upload and execute arbitrary PHP files as webshells. Upgrade ClipBucket immediately to version 5.5.1-239 or later, which implements strict file type validation and execution prevention. Review your server logs for suspicious file uploads in the playlist directory and remove any unauthorized PHP files.

sudo dnf update php

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST request to /upload.php or /admin/upload_playlist_cover.php with Content-Type: multipart/form-data containing files with .php, .phtml, .php5, .php7, .phar extensions disguised with image MIME types or double extensions like .php.jpg

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Block POST requests to playlist upload endpoints that contain executable file extensions (.php, .phtml, .php3, .php4, .php5, .php7, .phar, .phps, .pht). Implement MIME type validation requiring image/* content types only. Consider blocking requests where filename extension does not match declared Content-Type.

How to check if you are affected

  1. Check ClipBucket version: Access the admin panel and navigate to Settings > About to verify the installed version number
  2. Identify vulnerable installations: Search for ClipBucket installation directories (typically /var/www/html/clipbucket or /home/*/public_html/clipbucket) and check the version file at clipbucket/includes/config.php for VERSION constant
  3. Review upload logs: Examine web server access logs for POST requests to /upload.php or playlist-related endpoints with suspicious file extensions like .php, .phtml, .php5 in the request body
  4. Verify patch deployment: Confirm ClipBucket version is 5.5.1-239 or higher and check that file upload validation now rejects non-image MIME types in the playlist cover upload handler

FAQ

What is CVE-2025-21624?

This is a critical file upload vulnerability in ClipBucket's playlist cover image functionality that fails to validate uploaded file types, allowing attackers to upload malicious PHP files and gain remote code execution on the server.

Is CVE-2025-21624 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog and no public exploit code is currently available, but the critical CVSS score of 9.8 and ease of exploitation make it a high priority for immediate patching.

What versions of ClipBucket are affected by CVE-2025-21624?

All versions from 5.3 through 5.5.1-238 are vulnerable; the fix is available in ClipBucket 5.5.1-239 and later.

How do I check if my server is vulnerable to CVE-2025-21624?

Run: grep -r "VERSION" /path/to/clipbucket/includes/config.php | grep -E "5\.[3-4]|5\.5\.0|5\.5\.1-[0-2]" to identify vulnerable versions, or attempt to upload a test .php file to a playlist cover field and check if execution is blocked.

Does Defensia detect CVE-2025-21624?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If ClipBucket is installed on a monitored server, CVE-2025-21624 will appear in your dashboard with remediation steps.

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References

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