diff --git a/backend/Dockerfile b/backend/Dockerfile
index f23bb00..a11b743 100644
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1
 
 # ---- Build ------------------------------------------------------------------
-FROM eclipse-temurin:21-jdk-alpine AS build
+FROM eclipse-temurin:25-jdk-alpine AS build
 WORKDIR /src
 
 # Dependencies first, so source changes do not re-download them.
@@ -14,7 +14,7 @@ RUN --mount=type=cache,target=/root/.m2 ./mvnw -B -q package -DskipTests -Dspotl
  && java -Djarmode=tools -jar target/contester-api.jar extract --layers --launcher --destination /layers
 
 # ---- Runtime ----------------------------------------------------------------
-FROM eclipse-temurin:21-jre-alpine
+FROM eclipse-temurin:25-jre-alpine
 WORKDIR /app
 
 RUN addgroup -S -g 10001 app && adduser -S -u 10001 -G app app