CVE-2020-8437
📋 TL;DR
This vulnerability in uTorrent's bencoding parser allows remote attackers to cause denial of service by sending specially crafted nested bencoded dictionaries. It affects uTorrent users running vulnerable versions, potentially disrupting torrent client functionality.
💻 Affected Systems
- BitTorrent uTorrent
📦 What is this software?
Utorrent by Bittorrent
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service causing uTorrent to crash, potentially disrupting ongoing downloads/uploads and requiring manual restart.
Likely Case
Temporary service disruption when processing malicious torrent files or tracker responses, requiring application restart.
If Mitigated
Minimal impact with proper network segmentation and updated software.
🎯 Exploit Status
Exploitation requires sending malicious bencoded data to uTorrent, which could come from torrent files, tracker responses, or DHT nodes.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 3.5.5 (build 45505)
Vendor Advisory: https://forum.utorrent.com/forum/13-announcements/
Restart Required: Yes
Instructions:
1. Open uTorrent. 2. Go to Help > Check for Updates. 3. Install any available updates. 4. Restart uTorrent.
🔧 Temporary Workarounds
Network Segmentation
allRestrict uTorrent's network access to trusted sources only
Firewall Rules
allBlock incoming connections from untrusted sources
🧯 If You Can't Patch
- Disable DHT and PEX features to reduce attack surface
- Use alternative torrent clients that are not vulnerable
🔍 How to Verify
Check if Vulnerable:
Check uTorrent version in Help > About. If version is 3.5.5 or earlier (build 45505 or earlier), you are vulnerable.Check Version:
Not applicable - check via uTorrent GUI Help > AboutVerify Fix Applied:
Verify version is newer than 3.5.5 (build 45505) in Help > About.📡 Detection & Monitoring
Log Indicators:
- uTorrent crash logs
- unexpected termination events
- error messages related to bencoding parsing
Network Indicators:
- Unusual torrent file downloads
- malformed tracker responses
- suspicious DHT traffic
SIEM Query:
EventID: 1000 OR EventID: 1001 Source: uTorrent.exe AND (ExceptionCode: 0xc0000005 OR FaultingModule: utorrent.exe)🔗 References
- https://blog.whtaguy.com/2020/09/utorrent-cve-2020-8437-vulnerability.html
- https://forum.utorrent.com/forum/13-announcements/
- https://twitter.com/va_start
- https://utclient.utorrent.com/offers/beta_release_notes/release_notes.html
- https://blog.whtaguy.com/2020/09/utorrent-cve-2020-8437-vulnerability.html
- https://forum.utorrent.com/forum/13-announcements/
- https://twitter.com/va_start
- https://utclient.utorrent.com/offers/beta_release_notes/release_notes.html
