CVE-2025-53890
📋 TL;DR
An unsafe JavaScript evaluation vulnerability in pyLoad's CAPTCHA processing allows unauthenticated remote attackers to execute arbitrary code in client browsers and potentially the backend server. This can lead to session hijacking, credential theft, and full system compromise. All pyLoad instances running vulnerable versions are affected.
💻 Affected Systems
- pyLoad
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Full remote code execution on the pyLoad server, allowing complete system takeover, data exfiltration, and lateral movement within the network.
Likely Case
Client-side code execution leading to session hijacking, credential theft, and potential server compromise through chained attacks.
If Mitigated
Limited impact with proper network segmentation and isolation, potentially only affecting the pyLoad service itself.
🎯 Exploit Status
Exploitation requires no authentication or user interaction, making this highly dangerous.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.5.0b3.dev89 or later
Vendor Advisory: https://github.com/pyload/pyload/security/advisories/GHSA-8w3f-4r8f-pf53
Restart Required: Yes
Instructions:
1. Update pyLoad to version 0.5.0b3.dev89 or later. 2. Apply commit 909e5c97885237530d1264cfceb5555870eb9546. 3. Restart the pyLoad service.
🔧 Temporary Workarounds
Disable CAPTCHA functionality
allTemporarily disable CAPTCHA processing to prevent exploitation
Edit pyLoad configuration to disable CAPTCHA features
Network isolation
allRestrict access to pyLoad web interface
Configure firewall to block external access to pyLoad port
🧯 If You Can't Patch
- Immediately isolate the pyLoad instance from the internet and internal networks
- Disable the pyLoad service entirely until patching is possible
🔍 How to Verify
Check if Vulnerable:
Check if pyLoad version is earlier than 0.5.0b3.dev89 or if commit 909e5c97885237530d1264cfceb5555870eb9546 is not appliedCheck Version:
Check pyLoad web interface or configuration files for version informationVerify Fix Applied:
Verify pyLoad version is 0.5.0b3.dev89 or later and commit 909e5c97885237530d1264cfceb5555870eb9546 is present📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript execution in CAPTCHA processing logs
- Suspicious POST requests to CAPTCHA endpoints
Network Indicators:
- Unexpected outbound connections from pyLoad server
- Suspicious JavaScript payloads in HTTP requests
SIEM Query:
source="pyload" AND (event="captcha_processing" OR url="*captcha*") AND payload="*eval*" OR payload="*Function*"