CVE-2026-26999
📋 TL;DR
This vulnerability allows remote unauthenticated attackers to cause denial of service in Traefik by exploiting a TLS handshake flaw. Attackers can send incomplete TLS records to stall connections indefinitely, potentially exhausting system resources and degrading service availability. All systems running vulnerable versions of Traefik with TCP routers handling TLS connections are affected.
💻 Affected Systems
- Traefik
📦 What is this software?
Traefik by Traefik
Traefik by Traefik
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage on affected entrypoints due to resource exhaustion (file descriptors and goroutines), rendering all services behind the proxy unavailable.
Likely Case
Degraded performance and intermittent service disruptions as connections are held open, potentially causing timeouts and connection failures for legitimate users.
If Mitigated
Minimal impact with proper network controls, rate limiting, and monitoring in place to detect and block malicious connection attempts.
🎯 Exploit Status
Exploitation requires sending malformed TLS records and is relatively simple to implement. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.11.38 or 3.6.9
Vendor Advisory: https://github.com/traefik/traefik/security/advisories/GHSA-xw98-5q62-jx94
Restart Required: Yes
Instructions:
1. Identify your Traefik version. 2. If running version 2.x, upgrade to 2.11.38 or later. 3. If running version 3.x, upgrade to 3.6.9 or later. 4. Restart Traefik service to apply the patch.
🔧 Temporary Workarounds
Rate Limiting
allImplement connection rate limiting to prevent mass connection attempts
# Configure rate limiting in Traefik configuration or use external firewall/load balancer
Network Segmentation
allRestrict access to TCP routers to trusted networks only
# Use firewall rules to limit source IP addresses allowed to connect to Traefik TCP entrypoints
🧯 If You Can't Patch
- Implement strict network access controls to limit which clients can connect to Traefik TCP routers
- Deploy a Web Application Firewall (WAF) or reverse proxy in front of Traefik to filter malicious TLS connections
🔍 How to Verify
Check if Vulnerable:
Check Traefik version. If running version earlier than 2.11.38 (for v2) or 3.6.9 (for v3), the system is vulnerable.Check Version:
traefik versionVerify Fix Applied:
After patching, verify Traefik version shows 2.11.38 or higher (for v2) or 3.6.9 or higher (for v3). Monitor for stalled connections in logs.📡 Detection & Monitoring
Log Indicators:
- Unusually high number of stalled TLS connections
- Increased connection timeouts
- Resource exhaustion warnings
Network Indicators:
- Multiple incomplete TLS handshakes from single or distributed sources
- Abnormal connection duration patterns
SIEM Query:
source="traefik" AND ("TLS handshake error" OR "connection timeout" OR "stalled connection")