CVE-2025-53634
📋 TL;DR
CVE-2025-53634 is a denial-of-service vulnerability in Chall-Manager's HTTP Gateway that allows unauthenticated attackers to perform slow loris attacks due to missing timeout settings. Anyone who can reach the vulnerable Chall-Manager instance is affected. The vulnerability is particularly dangerous because it requires no authentication or authorization.
💻 Affected Systems
- Chall-Manager
📦 What is this software?
Chall Manager by Ctfer Io
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability of Chall-Manager, preventing all challenge management functionality and potentially affecting dependent services.
Likely Case
Degraded performance or temporary unavailability of Chall-Manager services during attack periods.
If Mitigated
Minimal impact if Chall-Manager is properly isolated within infrastructure as recommended, with no external access.
🎯 Exploit Status
Slow loris attacks are well-known and easy to implement. No authentication required makes exploitation trivial for anyone with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v0.1.4
Vendor Advisory: https://github.com/ctfer-io/chall-manager/security/advisories/GHSA-ggmv-j932-q89q
Restart Required: Yes
Instructions:
1. Update Chall-Manager to version 0.1.4 or later. 2. Restart the Chall-Manager service. 3. Verify the fix by checking the version and testing timeout behavior.
🔧 Temporary Workarounds
Network Isolation
allEnsure Chall-Manager is not directly accessible from untrusted networks as originally recommended.
Configure firewall rules to restrict access to Chall-Manager only from trusted IPs/networks
Reverse Proxy Timeout Configuration
linuxPlace Chall-Manager behind a reverse proxy with proper timeout settings.
nginx: proxy_read_timeout 60s;
apache: Timeout 60
🧯 If You Can't Patch
- Implement strict network access controls to limit who can reach the Chall-Manager service
- Deploy rate limiting and connection limiting at the network perimeter
🔍 How to Verify
Check if Vulnerable:
Check Chall-Manager version. If version is earlier than 0.1.4, it's vulnerable. Also test by sending slow HTTP requests to see if connections hang indefinitely.Check Version:
Check Chall-Manager logs or configuration for version information, or run the service with --version flag if availableVerify Fix Applied:
After updating to v0.1.4, test that HTTP connections timeout properly and cannot be held open indefinitely with slow loris techniques.📡 Detection & Monitoring
Log Indicators:
- Multiple long-duration HTTP connections from single sources
- Unusually slow request processing times
- Connection timeouts or service unavailability logs
Network Indicators:
- Multiple incomplete HTTP requests from same source
- Slow HTTP header transmissions
- Abnormally long-lived connections with minimal data transfer
SIEM Query:
source="chall-manager" AND (duration>300 OR (http.status="-" AND connection_time>60))