diff --git a/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/apacheweb/Dockerfile b/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/apacheweb/Dockerfile
index 0b6a7b19eba885..d3e266f4f7810d 100644
--- a/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/apacheweb/Dockerfile
+++ b/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/apacheweb/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:18.04
+FROM mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-20220421022739-9c434db
 
 ARG DEBIAN_FRONTEND=noninteractive
 
diff --git a/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/kdc/Dockerfile b/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/kdc/Dockerfile
index 1b28145ff833be..9abd3fa729d3ad 100644
--- a/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/kdc/Dockerfile
+++ b/src/libraries/Common/tests/System/Net/EnterpriseTests/setup/kdc/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:18.04
+FROM mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04-20220421022739-9c434db
 
 COPY ./kdc/kadm5.acl /etc/krb5kdc/
 COPY ./kdc/kdc.conf /etc/krb5kdc/