diff --git a/eng/pipelines/dotnet-core-nightly.yml b/eng/pipelines/dotnet-core-nightly.yml
index 4b230ebec9..a7ca51e430 100644
--- a/eng/pipelines/dotnet-core-nightly.yml
+++ b/eng/pipelines/dotnet-core-nightly.yml
@@ -47,6 +47,9 @@ resources:
 extends:
   template: /eng/docker-tools/templates/1es.yml@self
   parameters:
+    # Temporarily use only Permissive because CFSClean blocks Ubuntu/Debian package feeds.
+    # Tracking issue: https://github.com/dotnet/dotnet-docker-internal/issues/11529
+    networkIsolationPolicy: Permissive
     reposToExcludeFromScanning:
     - VersionsRepo
     stages:
diff --git a/eng/pipelines/dotnet-core.yml b/eng/pipelines/dotnet-core.yml
index 6acd4e4298..9bd9ece06f 100644
--- a/eng/pipelines/dotnet-core.yml
+++ b/eng/pipelines/dotnet-core.yml
@@ -34,6 +34,9 @@ resources:
 extends:
   template: /eng/docker-tools/templates/1es.yml@self
   parameters:
+    # Temporarily use only Permissive because CFSClean blocks Ubuntu/Debian package feeds.
+    # Tracking issue: https://github.com/dotnet/dotnet-docker-internal/issues/11529
+    networkIsolationPolicy: Permissive
     reposToExcludeFromScanning:
     - VersionsRepo
     stages: