CVE-2026-26999: Traefik TCP Router TLS Handshake Stalling Vulnerability
Summary
CVE-2026-26999: Impact There is a potential vulnerability in Traefik managing TLS handshake on TCP routers. Affects github.com/traefik/traefik/v2 versions < 2.11.38. Fixed in 2.11.38. How to fix ↓
Also tracked for
The same CVE-2026-26999 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Traefik is an open-source reverse proxy and load balancer designed to simplify the deployment of microservices. It automatically manages routing and load balancing for services, providing features like TLS termination, HTTP/2 support, and dynamic configuration. However, a vulnerability has been identified in its TCP router component that affects the handling of TLS handshakes, potentially leading to denial of service.
Vulnerability Detail
The vulnerability arises from Traefik clearing the read deadline for connections before completing the TLS handshake. This allows a remote unauthenticated attacker to send an incomplete TLS record and halt further data transmission, causing the handshake to stall indefinitely. As a result, the attacker can open multiple stalled connections, exhausting system resources such as file descriptors and goroutines, which degrades the availability of services on the affected entrypoint.
How To Fix
Latest published version: v2.11.60 as of 22 Oct 2026
go get github.com/traefik/traefik/v2@v2.11.60Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
2.11.38
This is the first release that contains the fix.
go get github.com/traefik/traefik/v2@v2.11.38Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
Currently, there are no workarounds available for this vulnerability. It is recommended to apply the patches as soon as possible to mitigate the risk.
Conclusion
In summary, CVE-2026-26999 is a significant vulnerability in Traefik's TCP router that can lead to denial of service through stalled TLS handshakes. It is essential to update to the latest patched versions to mitigate this risk and ensure the availability of your services.
See every vulnerability recorded for github.com/traefik/traefik/v2 →
FAQ
CVE-2026-26999 is a vulnerability in Traefik's TCP router that allows an attacker to stall TLS handshakes, leading to potential denial of service.
You can check if your application is affected by using Vulert, which monitors open-source vulnerabilities in real-time. Visit Vulert Scanner to analyze your application without any signup.
The vulnerability can lead to resource exhaustion, causing degraded availability of services due to stalled connections.
Yes, patches are available in Traefik versions v2.11.38 and v3.6.9. It is crucial to update to these versions.
The CVSS score of this vulnerability is 7.5, indicating a high severity level.
References
Related vulnerabilities
Recent vulnerabilities recorded for github.com/traefik/traefik/v2.
