CVE-2023-47633

The traefik docker container uses 100% CPU when it serves as its own backend, which is an automatically generated route resulting from the Docker integration in the default configuration.

Details

While attempting to set up Traefik to handle traffic for Docker containers, I observed in the webUI a rule with the following information:

Host(traefik-service) | webwebsecure | traefik-service@docker | traefik-service

I assumed that this is something internal; however, I wondered why it would have a host rule on the web entrypoint configured.

So I have send a request with that hostname with curl -v --resolve "traefik-service:80:xxx.xxx.xxx.xxx" http://traefik-service. That made my whole server unresponsive.

I assume the name comes from a docker container with that name, traefik itself:

localhost ~ # docker ps
CONTAINER ID   IMAGE                                                   COMMAND                  CREATED             STATUS         PORTS                                                                                                NAMES
d1414e74aec7   traefik:v2.10                                           "/entrypoint.sh trae…"   4 minutes ago       Up 4 minutes   0.0.0.0:80->80/tcp, :::80->80/tcp, 0.0.0.0:443->443/tcp, :::443->443/tcp, 127.0.0.1:8080->8080/tcp   traefik.service

PoC

1. Start traefik with docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -p 80:80 --name foo -p 8080:8080 traefik:v2.10 --api.insecure=true --providers.docker

2. curl -v --resolve "foo:80:127.0.0.1" http://foo

looks like this creates an endless loop of request.

Knowing the name of the docker container seems to be enough to trigger this, if the docker backend is used.

Server is unreachable and uses 100% CPU

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2023-47633 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.10.6, 3.0.0-beta5); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2023-47633? CVE-2023-47633 is a high-severity uncontrolled resource consumption vulnerability in github.com/traefik/traefik/v2 (go), affecting versions < 2.10.6. It is fixed in 2.10.6, 3.0.0-beta5. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2023-47633? CVE-2023-47633 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2023-47633?
   • github.com/traefik/traefik/v2 (go) (versions < 2.10.6)
   • github.com/traefik/traefik/v3 (go) (versions < 3.0.0-beta5)
4. Is there a fix for CVE-2023-47633? Yes. CVE-2023-47633 is fixed in 2.10.6, 3.0.0-beta5. Upgrade to this version or later.
5. Is CVE-2023-47633 exploitable, and should I be worried? Whether CVE-2023-47633 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-47633 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-47633?
   • Upgrade github.com/traefik/traefik/v2 to 2.10.6 or later
   • Upgrade github.com/traefik/traefik/v3 to 3.0.0-beta5 or later