diff --git a/Dockerfile b/Dockerfile
index 6253a8eaf..f1c462e28 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -70,7 +70,10 @@ COPY server/package.json ./server/
 # gypfile:false (npm/cli#9837). The only other install scripts among the runtime
 # deps are esbuild's binary check, redundant next to its optional platform
 # package, and a telemetry ping.
+# The upgrade takes the Debian security fixes the base image was built before
+# (zlib, 11/2026, failed the image scan until node:24-trixie-slim caught up).
 RUN apt-get update && \
+    apt-get upgrade -y --no-install-recommends && \
     apt-get install -y --no-install-recommends tzdata dumb-init wget ca-certificates \
     libkitinerary-bin libsqlite3-0 && \
     npm ci --workspace=server --omit=dev --ignore-scripts && \