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MCPX_DOCKER_SNAP_APPARMOR

Severity: warn Domain: Docker

What happened​

mcpproxy's security scanner sandbox launches the upstream stdio server inside a Docker container with --security-opt no-new-privileges and a pinned AppArmor profile. On Ubuntu's snap-installed Docker, AppArmor's profile transition combined with no-new-privileges causes every command in the container to fail with operation not permitted — the scanner can't run.

This is a known incompatibility between snap Docker's AppArmor confinement and the security flags mcpproxy needs for the scanner. Other (non-scanner) Docker isolation works fine.

How to fix​

You have three options:

sudo snap remove docker
# Then install Docker Desktop, Colima, or rootless Docker
# https://docs.docker.com/engine/install/ubuntu/

2. Disable the scanner for this server (dry-run shown by default)​

The error panel includes a Disable scanner for this server fix-step. The CLI equivalent:

mcpproxy upstream patch <server-name> --no-scanner --dry-run

Drop --dry-run to apply. The server will still run with isolation, but without TPA pre-flight scanning.

3. Run mcpproxy without isolation for that server​

If you trust the upstream and don't need isolation:

{ "isolation": { "enabled": false } }

Background​

See scanner snap-docker AppArmor incompatibility for the upstream tracking issue.