diff --git a/.github/workflows/ca-trust.yml b/.github/workflows/ca-trust.yml
new file mode 100644
index 0000000..c585bcd
--- /dev/null
+++ b/.github/workflows/ca-trust.yml
@@ -0,0 +1,19 @@
+name: CA trust
+on:
+  pull_request:
+  push:
+    branches: [main]
+permissions:
+  contents: read
+jobs:
+  trust:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+      - name: Regression tests with public CA fixtures
+        run: node --test scripts/ca-trust.test.mjs
+      - run: docker build --pull --target base -t ca-voterr .
+      - run: docker run --rm --entrypoint sh -v "$PWD/scripts:/checks:ro" ca-voterr /checks/check-ca-trust.sh /checks/ca-fixtures
diff --git a/Dockerfile b/Dockerfile
index f8e43f2..6e2d81c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,6 +4,13 @@
 ARG RUBY_VERSION=3.3.12
 FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
 
+# Apply the October 2026 CA distrust before Bundler or app HTTPS requests.
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y ca-certificates openssl && \
+    rm -rf /var/lib/apt/lists/*
+COPY scripts/distrust-compromised-cas.sh /usr/local/bin/distrust-compromised-cas
+RUN sh /usr/local/bin/distrust-compromised-cas && update-ca-certificates --fresh
+
 # Rails app lives here
 WORKDIR /rails
 
@@ -60,3 +67,4 @@ ENTRYPOINT ["/rails/bin/docker-entrypoint"]
 # Start the server by default, this can be overwritten at runtime
 EXPOSE 3000
 CMD ["./bin/rails", "server"]
+
diff --git a/docs/ca-trust-incident.md b/docs/ca-trust-incident.md
new file mode 100644
index 0000000..337cf3b
--- /dev/null
+++ b/docs/ca-trust-incident.md
@@ -0,0 +1,51 @@
+# October 2026 eMudhra CA incident
+
+The reviewed outbound clients use normal TLS verification: Plex uses Faraday and TMDB uses Net::HTTP. Normal verification
+is insufficient when its root store still permits the compromised CA hierarchy.
+This change updates trust in images; it does not establish whether any running
+deployment was attacked.
+
+The build disables these trust anchors by exact SHA-256 fingerprint:
+- emSign ECC Root CA - G3: `86a1ecba089c4a8d3bbe2734c612ba341d813e043cf9e8a862cd5c57a36bbe6b`
+- emSign Root TLS CA - G3, self-signed: `7dd78d5f4f13459a83dff9abbba62edbaf6f2d102bf257fd712f4d9f2746ed8d`
+- emSign Root TLS CA - G3, cross-signed: `3094025792039a68af6e553686410bdab7c0d4a36b9084cba64202e35d6ebbdd`
+- AAA Certificate Services: `d7a7a0fb5d7e2731d771e9484ebcdef71d5f0c3e0a2948782bc83ee0ea699ef4`
+
+AAA is a retired root with an alternate signing path to the compromised
+intermediates. Leaving it in an older distro bundle can defeat removal of just
+the eMudhra root. Other emSign roots and USERTrust/Sectigo roots are preserved.
+Valid sites that still depend on the removed hierarchies can stop connecting;
+their operators must move to an unaffected chain. Do not bypass verification.
+
+The script scans distribution and locally imported CA sources, disables matching
+configuration entries, and moves blocked certificates outside the *.crt import
+glob. `update-ca-certificates --fresh` then regenerates both the bundle and
+hashed directory, so clients cannot fall back to an old hashed certificate.
+A malformed source certificate fails the build. Re-running is safe.
+
+## Deployment
+
+The shared Ruby base applies distrust before Bundler installs and is inherited
+by the final runtime. Rebuild with `docker build --pull --no-cache -t voterr:patched .`
+and deploy the resulting image through the normal hosting workflow.
+
+Existing containers do not change when the PR is merged. Rebuild and redeploy.
+For native development, update the host/runtime CA store separately. Custom
+application CA options, mounted bundles, and trust-related environment overrides
+must be audited separately; this build does not rewrite external files.
+
+## Validation
+
+Run `node --test scripts/ca-trust.test.mjs` (Node 22+, OpenSSL on PATH).
+Fixtures are public CA certificates with no private keys. Tests cover renamed
+and duplicate blocked certificates, local imports, idempotence, preservation of
+ISRG Root X1, actual OpenSSL rejection, and failure on corrupt input.
+CI also runs `scripts/check-ca-trust.sh` against built image trust stores.
+A package vulnerability scan alone does not prove that an application rejects
+a compromised chain.
+
+## References
+
+- [Mozilla incident and alternate cross-signs](https://bugzilla.mozilla.org/show_bug.cgi?id=2083449)
+- [eMudhra certificate repository and fingerprints](https://repository.emsign.com/)
+- [Historical Mozilla-derived AAA certificate fingerprint](https://android.googlesource.com/platform/system/ca-certificates/+/5a9e1c65f159e4a8461bf646aa116001e2844516/google/roots.pem)
diff --git a/scripts/ca-fixtures/aaa.pem b/scripts/ca-fixtures/aaa.pem
new file mode 100644
index 0000000..33c71ba
--- /dev/null
+++ b/scripts/ca-fixtures/aaa.pem
@@ -0,0 +1,25 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/scripts/ca-fixtures/emsign.pem b/scripts/ca-fixtures/emsign.pem
new file mode 100644
index 0000000..63637d8
--- /dev/null
+++ b/scripts/ca-fixtures/emsign.pem
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
diff --git a/scripts/ca-fixtures/isrg.pem b/scripts/ca-fixtures/isrg.pem
new file mode 100644
index 0000000..c0c7e62
--- /dev/null
+++ b/scripts/ca-fixtures/isrg.pem
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/scripts/ca-trust.test.mjs b/scripts/ca-trust.test.mjs
new file mode 100644
index 0000000..e9e1023
--- /dev/null
+++ b/scripts/ca-trust.test.mjs
@@ -0,0 +1,64 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { mkdtempSync, mkdirSync, readFileSync, writeFileSync, existsSync, readdirSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { spawnSync } from "node:child_process";
+
+const here = fileURLToPath(new URL(".", import.meta.url));
+const script = join(here, "distrust-compromised-cas.sh");
+const fixture = (name) => readFileSync(join(here, "ca-fixtures", name + ".pem"), "utf8");
+const run = (cmd, args) => spawnSync(cmd, args, { encoding: "utf8" });
+
+test("distrusts renamed G3/AAA anchors, preserves unrelated roots, and is idempotent", () => {
+  const root = mkdtempSync(join(tmpdir(), "ca-distrust-"));
+  try {
+    const ca = join(root, "usr/share/ca-certificates/mozilla");
+    const local = join(root, "usr/local/share/ca-certificates");
+    mkdirSync(ca, { recursive: true });
+    mkdirSync(local, { recursive: true });
+    mkdirSync(join(root, "etc"));
+    writeFileSync(join(ca, "renamed.crt"), fixture("emsign"));
+    writeFileSync(join(ca, "keep.crt"), fixture("isrg"));
+    writeFileSync(join(local, "legacy-cross-sign-root.crt"), fixture("aaa"));
+    // An imported duplicate must not restore trust.
+    writeFileSync(join(local, "duplicate.crt"), fixture("emsign"));
+    writeFileSync(join(root, "etc/ca-certificates.conf"), "# preserve comments\nmozilla/renamed.crt\nmozilla/keep.crt\n");
+    for (let i = 0; i < 2; i++) {
+      const result = run("sh", [script, root]);
+      assert.equal(result.status, 0, result.stderr);
+    }
+    assert.equal(existsSync(join(ca, "renamed.crt")), false);
+    assert.equal(existsSync(join(local, "legacy-cross-sign-root.crt")), false);
+    assert.equal(existsSync(join(local, "duplicate.crt")), false);
+    assert.equal(readFileSync(join(ca, "keep.crt"), "utf8"), fixture("isrg"));
+    assert.equal(readFileSync(join(root, "etc/ca-certificates.conf"), "utf8"),
+      "# preserve comments\n!mozilla/renamed.crt\nmozilla/keep.crt\n");
+
+    const bundle = join(root, "filtered.pem");
+    writeFileSync(bundle, readdirSync(ca).filter(p => p.endsWith(".crt")).map(p => readFileSync(join(ca, p), "utf8")).join("\n"));
+    // -trusted isolates the fixture anchors, including on OpenSSL 3 where
+    // -CAfile/-CApath alone can still consult the default CAstore.
+    const args = ["verify", "-trusted", bundle];
+    assert.equal(run("openssl", [...args, join(here, "ca-fixtures/isrg.pem")]).status, 0);
+    for (const name of ["emsign", "aaa"]) {
+      const result = run("openssl", [...args, join(here, "ca-fixtures", name + ".pem")]);
+      assert.notEqual(result.status, 0, name + " must be distrusted: " + result.stdout + result.stderr);
+    }
+  } finally {
+    rmSync(root, { recursive: true, force: true });
+  }
+});
+
+test("fails on a malformed CA instead of silently leaving it trusted", () => {
+  const root = mkdtempSync(join(tmpdir(), "ca-invalid-"));
+  try {
+    const ca = join(root, "usr/share/ca-certificates");
+    mkdirSync(ca, { recursive: true });
+    writeFileSync(join(ca, "bad.crt"), "not a certificate");
+    assert.notEqual(run("sh", [script, root]).status, 0);
+  } finally {
+    rmSync(root, { recursive: true, force: true });
+  }
+});
diff --git a/scripts/check-ca-trust.sh b/scripts/check-ca-trust.sh
new file mode 100644
index 0000000..ee148ff
--- /dev/null
+++ b/scripts/check-ca-trust.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+# Check the actual regenerated bundle AND hashed CA directory in a built image.
+set -eu
+fixtures=${1:?usage: check-ca-trust.sh fixture-directory}
+openssl verify -CAfile /etc/ssl/certs/ca-certificates.crt -CApath /etc/ssl/certs "$fixtures/isrg.pem"
+for cert in emsign aaa; do
+    openssl x509 -in "$fixtures/$cert.pem" -noout >/dev/null
+    if openssl verify -CAfile /etc/ssl/certs/ca-certificates.crt -CApath /etc/ssl/certs "$fixtures/$cert.pem"; then
+        echo "ERROR: blocked $cert anchor is still trusted" >&2
+        exit 1
+    fi
+done
+if command -v node >/dev/null 2>&1; then
+    node -e 'if (!(process.env.NODE_OPTIONS || "").split(/\s+/).includes("--use-openssl-ca")) throw new Error("Node must use the filtered OpenSSL trust store")'
+fi
diff --git a/scripts/distrust-compromised-cas.sh b/scripts/distrust-compromised-cas.sh
new file mode 100644
index 0000000..60bcff5
--- /dev/null
+++ b/scripts/distrust-compromised-cas.sh
@@ -0,0 +1,43 @@
+#!/bin/sh
+# Disable the eMudhra G3 hierarchies and the retired AAA cross-signing root.
+# Incident: https://bugzilla.mozilla.org/show_bug.cgi?id=2083449
+# Fingerprints: https://repository.emsign.com/ and Mozilla's historical root store.
+# Run before update-ca-certificates --fresh. No network access is required.
+set -eu
+
+root=${1:-/}
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT HUP INT TERM
+: > "$work/disabled"
+
+for dir in "$root/usr/share/ca-certificates" "$root/usr/local/share/ca-certificates"; do
+    [ ! -d "$dir" ] || find "$dir" -type f -name '*.crt' >> "$work/files"
+done
+[ -f "$work/files" ] || { echo "No CA source directories found" >&2; exit 1; }
+
+while IFS= read -r cert; do
+    # Do not hide openssl errors behind a pipeline: a corrupt CA must fail the build.
+    fingerprint=$(openssl x509 -in "$cert" -noout -sha256 -fingerprint)
+    fingerprint=$(printf '%s' "$fingerprint" | cut -d= -f2 | tr -d ':' | tr 'A-F' 'a-f')
+    case "$fingerprint" in
+        # emSign ECC G3, TLS G3 (both variants), and AAA Certificate Services.
+        86a1ecba089c4a8d3bbe2734c612ba341d813e043cf9e8a862cd5c57a36bbe6b|\
+        7dd78d5f4f13459a83dff9abbba62edbaf6f2d102bf257fd712f4d9f2746ed8d|\
+        3094025792039a68af6e553686410bdab7c0d4a36b9084cba64202e35d6ebbdd|\
+        d7a7a0fb5d7e2731d771e9484ebcdef71d5f0c3e0a2948782bc83ee0ea699ef4)
+            relative=${cert#"$root/usr/share/ca-certificates/"}
+            printf '%s\n' "$relative" >> "$work/disabled"
+            # Keep the public cert for inspection, outside the *.crt import glob.
+            mv "$cert" "$cert.distrusted"
+            echo "Distrusted CA: $fingerprint" >&2
+            ;;
+    esac
+done < "$work/files"
+
+conf="$root/etc/ca-certificates.conf"
+if [ -f "$conf" ]; then
+    awk 'FILENAME == ARGV[1] { blocked[$0] = 1; next }
+         { if ($0 in blocked) print "!" $0; else print }' \
+        "$work/disabled" "$conf" > "$work/config"
+    cat "$work/config" > "$conf"
+fi