CVE-2025-55911
📋 TL;DR
This vulnerability in ClipBucket v5.5.2 Build#90 allows remote attackers to execute arbitrary code via the file_downloader.php component by manipulating the file parameter. It affects all systems running this specific vulnerable version of ClipBucket, potentially compromising web servers and their data.
💻 Affected Systems
- ClipBucket
📦 What is this software?
Clipbucket by Oxygenz
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise leading to data theft, ransomware deployment, or use as a foothold for lateral movement within the network.
Likely Case
Unauthorized file access, data exfiltration, and potential privilege escalation on the affected web server.
If Mitigated
Limited impact with proper network segmentation, web application firewalls, and minimal privileges reducing potential damage.
🎯 Exploit Status
The Medium article describes SSRF exploitation via upload actions, suggesting attackers need to chain multiple steps for full RCE. No public exploit code is available yet.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after v5.5.2 Build#90
Vendor Advisory: https://medium.com/@mukund.s1337/cve-2025-55911-clipbucket-5-5-2-build-90-ssrf-via-upload-actions-file-downloader-php-eb49dc02bd6f
Restart Required: No
Instructions:
1. Upgrade ClipBucket to the latest version. 2. If upgrade isn't possible, apply the specific patch for file_downloader.php. 3. Remove or restrict access to vulnerable file_downloader.php if not needed.
🔧 Temporary Workarounds
Restrict file_downloader.php access
allBlock direct access to the vulnerable file_downloader.php script using web server configuration or firewall rules.
# Apache: RewriteRule ^file_downloader\.php$ - [F]
# Nginx: location ~ /file_downloader\.php$ { deny all; }
Input validation hardening
allAdd strict input validation for the file parameter in file_downloader.php to prevent path traversal and SSRF.
# In file_downloader.php, validate file parameter: if (!preg_match('/^[a-zA-Z0-9_\-\.]+$/', $_GET['file'])) { die('Invalid file'); }
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ClipBucket server from critical systems.
- Deploy a web application firewall (WAF) with rules to block malicious requests to file_downloader.php.
🔍 How to Verify
Check if Vulnerable:
Check if ClipBucket version is exactly v5.5.2 Build#90 and if file_downloader.php exists in the installation directory.Check Version:
grep -r 'ClipBucket.*5\.5\.2.*Build#90' /path/to/clipbucket/installation/Verify Fix Applied:
Verify the ClipBucket version has been updated beyond v5.5.2 Build#90 and test that file_downloader.php no longer accepts malicious file parameters.📡 Detection & Monitoring
Log Indicators:
- Unusual requests to file_downloader.php with suspicious file parameters
- Multiple failed attempts to access restricted files via file_downloader.php
Network Indicators:
- Unexpected outbound connections from web server to internal systems following file_downloader.php requests
- Traffic patterns suggesting SSRF attempts
SIEM Query:
source="web_server_logs" AND uri="/file_downloader.php" AND (file="*../*" OR file="*://*")