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How to harden a RethinkDB container (and is rethinkdb:2.4 safe for untrusted workloads?)

A realtime document database pushes query results straight to connected clients, so the process sits close to your application data and deserves a tight container. A stock docker run rethinkdb:2.4 is not: graded on IronClaw's seven-dimension containment scale it scores 48 of 100, grade D (porous). Higher is safer. A short list of runtime flags takes the same image to 100 of 100, grade A, because a single-node RethinkDB that only its co-located app queries can drop its network entirely. Here are the exact gaps and fixes from the scan data.

Graded from a read-only inspect of a running container started from rethinkdb:2.4 with plain docker run defaults, its entrypoint overridden with sleep purely to keep it alive. The scan itself executes nothing inside the container. It is the same data behind its isolation scorecard. How scoring works →

Where the default configuration leaks

ironctl scan grades seven independent containment boundaries. On a default docker run rethinkdb:2.4, four fail or warn:

Dimension Verdict Score What the scan found
Non-root user (uid != 0) ❌ FAIL 0/15 runs as root (uid 0); a container escape starts with host-uid 0
Dropped capabilities ❌ FAIL 4/20 default capability set retained (CAP_NET_RAW, CAP_MKNOD, and more)
Seccomp profile ✅ PASS 15/15 seccomp profile active
Network isolation / egress ⚠️ WARN 4/15 network=bridge: outbound egress is possible
Read-only root filesystem ❌ FAIL 0/10 root filesystem is writable
No docker.sock exposure ✅ PASS 15/15 no control socket mounted
No shared host namespaces ✅ PASS 10/10 no host PID/IPC/network sharing

The sharpest edges are root, the retained capabilities, and the writable rootfs: a ReQL-parser or driver CVE that lands code execution lands it as uid 0, with CAP_NET_RAW and friends, on a filesystem it can rewrite to persist.

Harden it: the exact --fix remediation

ironctl scan my-rethinkdb --fix prints one remediation per failed dimension, then one hardened run. For rethinkdb:2.4:

  • --user 65532:65532 (Non-root, +15): run the process as an unprivileged uid. Point the data directory (/data) at a volume that uid owns.
  • --cap-drop=ALL (Dropped capabilities, +16): drop every Linux capability; add back only what the workload provably needs. RethinkDB needs none of the defaults.
  • --read-only --tmpfs /tmp (Read-only rootfs, +10): make the root filesystem read-only and mount /data as an explicit writable volume. Removes the persistence surface.
  • --network=none (Network isolation, +11): a single-node document database that only its co-located app queries needs no external network at all. Attach it to app services over a private compose network and cut the default route out. This is the dimension that takes it to a full A.

Before and after

# Before: 48/100, grade D
docker run -d --name rethinkdb rethinkdb:2.4

# After: 100/100, grade A
docker run -d --name rethinkdb-hardened \
  --user 65532:65532 \
  --cap-drop=ALL \
  --security-opt=no-new-privileges \
  --read-only --tmpfs /tmp \
  -v rethinkdb-data:/data \
  --network=none \
  rethinkdb:2.4

Rescan: ironctl scan rethinkdb-hardened reports 100/100 grade A. A 52-point swing with no custom image build, just the right flags.

Running a cluster? A multi-node RethinkDB (peers joined over the cluster port, or remote drivers) needs the nodes to reach each other, so --network=none is wrong there. Keep the other four fixes and attach a scoped private network; the honest ceiling is then 89/100, grade B, with the network dimension held at a WARN. Single-node with a co-located app reaches the full A.

Verify it on your own database

# install (Homebrew)
brew install ironsecco/ironclaw/ironclaw

# grade your running container, then print the fixes
ironctl scan my-rethinkdb
ironctl scan my-rethinkdb --fix

ironctl scan also reads a docker-compose.yml service or a Kubernetes manifest, so you can grade the RethinkDB in your stack, not just a bare docker run.

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