diff --git a/xds/src/main/java/io/grpc/xds/XdsEndpointResource.java b/xds/src/main/java/io/grpc/xds/XdsEndpointResource.java
index 2a44b5f297b..e57113ef189 100644
--- a/xds/src/main/java/io/grpc/xds/XdsEndpointResource.java
+++ b/xds/src/main/java/io/grpc/xds/XdsEndpointResource.java
@@ -22,6 +22,7 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.net.InetAddresses;
+import com.google.common.primitives.UnsignedInteger;
 import com.google.protobuf.Any;
 import com.google.protobuf.InvalidProtocolBufferException;
 import com.google.protobuf.Message;
@@ -115,6 +116,7 @@ private static boolean isEnabledXdsDualStack() {
   private static EdsUpdate processClusterLoadAssignment(ClusterLoadAssignment assignment)
       throws ResourceInvalidException {
     Map<Integer, Set<Locality>> priorities = new HashMap<>();
+    Map<Integer, Long> localityWeightSums = new HashMap<>();
     Map<Locality, LocalityLbEndpoints> localityLbEndpointsMap = new LinkedHashMap<>();
     Set<java.net.SocketAddress> endpointAddresses = new HashSet<>();
     List<Endpoints.DropOverload> dropOverloads = new ArrayList<>();
@@ -133,6 +135,14 @@ private static EdsUpdate processClusterLoadAssignment(ClusterLoadAssignment assi
       LocalityLbEndpoints localityLbEndpoints = structOrError.getStruct();
       int priority = localityLbEndpoints.priority();
       maxPriority = Math.max(maxPriority, priority);
+      long localityWeightSum = localityWeightSums.getOrDefault(priority, 0L)
+          + localityLbEndpoints.localityWeight();
+      if (localityWeightSum > UnsignedInteger.MAX_VALUE.longValue()) {
+        throw new ResourceInvalidException(
+            "Sum of weights of localities at the same priority " + priority
+                + " exceeded maximal value");
+      }
+      localityWeightSums.put(priority, localityWeightSum);
       // Note endpoints with health status other than HEALTHY and UNKNOWN are still
       // handed over to watching parties. It is watching parties' responsibility to
       // filter out unhealthy endpoints. See EnvoyProtoData.LbEndpoint#isHealthy().
diff --git a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
index dc9590aed51..418a7457564 100644
--- a/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
+++ b/xds/src/test/java/io/grpc/xds/GrpcXdsClientImplDataTest.java
@@ -1080,6 +1080,39 @@ public void parseLocalityLbEndpoints_withHealthyEndpoints() throws ResourceInval
             100, 1, ImmutableMap.of()));
   }
 
+  @Test
+  public void processClusterLoadAssignment_localityWeightSumExceedsUint32Max() {
+    // Sum of locality weights at priority 1 is 2147483647 + 2147483647 + 2 = 4294967296.
+    io.envoyproxy.envoy.config.endpoint.v3.ClusterLoadAssignment assignment =
+        io.envoyproxy.envoy.config.endpoint.v3.ClusterLoadAssignment.newBuilder()
+            .setClusterName("cluster-foo")
+            .addEndpoints(buildLocalityLbEndpoints("region1", "172.14.14.1", 1, 0))
+            .addEndpoints(buildLocalityLbEndpoints("region2", "172.14.14.2", Integer.MAX_VALUE, 1))
+            .addEndpoints(buildLocalityLbEndpoints("region3", "172.14.14.3", Integer.MAX_VALUE, 1))
+            .addEndpoints(buildLocalityLbEndpoints("region4", "172.14.14.4", 2, 1))
+            .build();
+    ResourceInvalidException ex = assertThrows(
+        ResourceInvalidException.class,
+        () -> XdsEndpointResource.getInstance().doParse(getXdsResourceTypeArgs(true), assignment));
+    assertThat(ex).hasMessageThat().isEqualTo(
+        "Sum of weights of localities at the same priority 1 exceeded maximal value");
+  }
+
+  private static io.envoyproxy.envoy.config.endpoint.v3.LocalityLbEndpoints
+      buildLocalityLbEndpoints(String region, String address, int localityWeight, int priority) {
+    return io.envoyproxy.envoy.config.endpoint.v3.LocalityLbEndpoints.newBuilder()
+        .setLocality(Locality.newBuilder().setRegion(region))
+        .setLoadBalancingWeight(UInt32Value.of(localityWeight))
+        .setPriority(priority)
+        .addLbEndpoints(io.envoyproxy.envoy.config.endpoint.v3.LbEndpoint.newBuilder()
+            .setEndpoint(Endpoint.newBuilder()
+                .setAddress(Address.newBuilder()
+                    .setSocketAddress(
+                        SocketAddress.newBuilder().setAddress(address).setPortValue(8888))))
+            .setHealthStatus(io.envoyproxy.envoy.config.core.v3.HealthStatus.HEALTHY))
+        .build();
+  }
+
   @Test
   public void parseLocalityLbEndpoints_onlyPermitIp() {
     io.envoyproxy.envoy.config.endpoint.v3.LocalityLbEndpoints proto =