CVE-2024-45410

Traefik is a golang, Cloud Native Application Proxy. When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified. For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been addressed in release versions 2.11.9 and 3.1.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Traefik is a golang, Cloud Native Application Proxy. When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified. For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been addressed in release versions 2.11.9 and 3.1.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Impact

There is a vulnerability in Traefik that allows the client to remove the X-Forwarded headers (except the header X-Forwarded-For).

Patches

• https://github.com/traefik/traefik/releases/tag/v2.11.9
• https://github.com/traefik/traefik/releases/tag/v3.1.3

Workarounds

No workaround.

For more information

If you have any questions or comments about this advisory, please open an issue.

<details> <summary>Original Description</summary> ### Summary

When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified.

For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. By setting the following connection header, the X-Forwarded-Host header can, for example, be removed:

Connection: close, X-Forwarded-Host

Depending on how the receiving application handles such cases, security implications may arise. Moreover, some application frameworks (e.g. Django) first transform the "-" to "_" signs, making it possible for the HTTP client to even modify these headers in these cases.

This is similar to CVE-2022-31813 for Apache HTTP Server.

Details

It was found that the following headers can be removed in this way (i.e. by specifing them within a connection header):

• X-Forwarded-Host
• X-Forwarded-Port
• X-Forwarded-Proto
• X-Forwarded-Server
• X-Real-Ip
• X-Forwarded-Tls-Client-Cert
• X-Forwarded-Tls-Client-Cert-Info

PoC

The following docker-compose file has been used for a simple setup:

services:
  traefik:
    image: traefik:v3.1
    container_name: traefik
    ports:
      - "443:443"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - ./traefik.yaml:/etc/traefik/traefik.yaml
      - ./traefik-certs:/certs

  python-http:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: python-http
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.python-http.rule=Host(`python.example.com`)"
      - "traefik.http.routers.python-http.entrypoints=websecure"
      - "traefik.http.routers.python-http.tls=true"
      - "traefik.http.services.python-http.loadbalancer.server.port=8080"

The following traefik.yaml has been used:

providers:
  docker:
    exposedByDefault: false
    watch: true
  file:
    fileName: /etc/traefik/traefik.yaml
    watch: true

entryPoints:
  websecure:
    address: ":443"

tls:
  certificates:
    - certFile: /certs/server-cert.pem
      keyFile: /certs/server-key.pem

The Python container just includes a simple Python HTTP server that prints the HTTP headers it receives. Here is the Dockerfile for the container:

FROM python:3-alpine

# Copy the Python script to the container
COPY server.py /server.py

# Set the working directory
WORKDIR /

# Command to run the Python server
CMD ["python", "/server.py"]

And here is the Python script:

from http.server import BaseHTTPRequestHandler, HTTPServer

class RequestHandler(BaseHTTPRequestHandler):
    def _send_response(self):
        self.send_response(200)
        self.send_header("Content-type", "text/plain")
        self.end_headers()
        self.wfile.write(str(self.headers).encode("utf-8"))

    def do_GET(self):
        self._send_response()

if __name__ == "__main__":
    server = HTTPServer(('0.0.0.0', 8080), RequestHandler)
    print("Server started on port 8080")
    server.serve_forever()

The environment is run with sudo docker-compose up.

A…

Traefik is a golang, Cloud Native Application Proxy. When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified. For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been addressed in release versions 2.11.9 and 3.1.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Traefik is a golang, Cloud Native Application Proxy. When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified. For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been addressed in release versions 2.11.9 and 3.1.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Traefik is a golang, Cloud Native Application Proxy. When a HTTP request is processed by Traefik, certain HTTP headers such as X-Forwarded-Host or X-Forwarded-Port are added by Traefik before the request is routed to the application. For a HTTP client, it should not be possible to remove or modify these headers. Since the application trusts the value of these headers, security implications might arise, if they can be modified. For HTTP/1.1, however, it was found that some of theses custom headers can indeed be removed and in certain cases manipulated. The attack relies on the HTTP/1.1 behavior, that headers can be defined as hop-by-hop via the HTTP Connection header. This issue has been addressed in release versions 2.11.9 and 3.1.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.