diff --git a/Dockerfile b/Dockerfile
index 0dcd726..8eff964 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,18 +1,19 @@
-FROM alpine:3.18
+FROM alpine:3.21
 
 RUN \
-  apk -U add rsyslog rsyslog-mmutf8fix
+  apk --no-cache upgrade && \
+  apk --no-cache add rsyslog rsyslog-mmutf8fix
 
 COPY run.sh /
 
 EXPOSE 514/tcp
 EXPOSE 514/udp
 
-ENV TARGET_HOST="127.0.0.1"
-ENV TARGET_PROTO="tcp"
-ENV TARGET_PORT="514"
-ENV DEBUG="0"
+ENV TARGET_HOST="127.0.0.1" \
+    TARGET_PROTO="tcp" \
+    TARGET_PORT="514" \
+    DEBUG="0"
 
 VOLUME [ "/extraconfig" ]
 
-ENTRYPOINT ["/bin/sh", "/run.sh"]
\ No newline at end of file
+ENTRYPOINT ["/bin/sh", "/run.sh"]