[🐛 Bug]: Firefox WebDriver hangs on quit - if firefox runs on partly-isolated host

What happened?

While the chrome webdriver works without problems, the firefox webdriver hangs on .quit() with a communication error with marionette.

Our selenium-server is in a partly-seperated net - it only has webaccess to local web servers, but not to the internet.

We moved the VM to an open net - and the firefox webdriver quits without problems. Then we installed tcpdump in selenoid_node_all and observed that the container tries to connect to 146.75.121.91:443 while quitting. Because this packages gets discarded at our firewall, the VM hangs and quit() is not successfull.

So: Why is firefox or firefox webdriver connecting to this IP? It seems to be some kind of Fastly Geolocation?

Is it possible to switch any connections to external services off?

Command used to start Selenium Grid with Docker (or Kubernetes)

services:
  selenium_hub:
    image: selenium/hub:4.45.0-20260606
    container_name: selenium_hub
    ports:
      - "127.0.0.1:4444:4444"
    expose:
      - 4442
      - 4443

  selenium_node_all:
    shm_size: 3gb
    depends_on: 
      - selenium_hub
    image: selenium/node-all-browsers:4.45.0
    container_name: selenium_node_all
    environment:
      - SE_EVENT_BUS_HOST=selenium_hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443
      - SE_LOG_LEVEL=FINE
      - SE_OPTS=--log-level FINE

Relevant log output

Output of tcpdump:

08:30:59.668254 IP (tos 0x0, ttl 64, id 31691, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44638 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0xbc34), seq 1011157030, win 64240, options [mss 1460,sackOK,TS val 2908501820 ecr 0,nop,wscale 7], length 0
08:30:59.924254 IP (tos 0x0, ttl 64, id 26637, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44640 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0x5f96), seq 1768437407, win 64240, options [mss 1460,sackOK,TS val 2908502076 ecr 0,nop,wscale 7], length 0
08:31:00.692306 IP (tos 0x0, ttl 64, id 31692, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44638 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0xb834), seq 1011157030, win 64240, options [mss 1460,sackOK,TS val 2908502844 ecr 0,nop,wscale 7], length 0
08:31:00.948308 IP (tos 0x0, ttl 64, id 26638, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44640 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0x5b96), seq 1768437407, win 64240, options [mss 1460,sackOK,TS val 2908503100 ecr 0,nop,wscale 7], length 0
08:31:01.716308 IP (tos 0x0, ttl 64, id 31693, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44638 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0xb434), seq 1011157030, win 64240, options [mss 1460,sackOK,TS val 2908503868 ecr 0,nop,wscale 7], length 0
08:31:01.972311 IP (tos 0x0, ttl 64, id 26639, offset 0, flags [DF], proto TCP (6), length 60)
    7b093e42dfd9.44640 > 146.75.121.91.443: Flags [S], cksum 0xb7eb (incorrect -> 0x5796), seq 1768437407, win 64240, options [mss 1460,sackOK,TS val 2908504124 ecr 0,nop,wscale 7], length 0

Operating System

Ubuntu

Docker Selenium version (image tag)

4.45.0-20260606

Selenium Grid chart version (chart version)

No response

Start with the Firefox WebDriver/Marionette shutdown path and the tcpdump output from the selenium_node_all container. Reproduce using the supplied selenium/node-all-browsers:4.45.0 image on a restricted network, compare it with an open network, and identify the service behind 146.75.121.91:443. Done means quit() completes without external access, or the required configuration to disable that connection is documented.