diff --git a/common/src/main/java/org/apache/rocketmq/common/utils/NameServerAddressUtils.java b/common/src/main/java/org/apache/rocketmq/common/utils/NameServerAddressUtils.java
index 68f883935ae..86c4ea3f8a3 100644
--- a/common/src/main/java/org/apache/rocketmq/common/utils/NameServerAddressUtils.java
+++ b/common/src/main/java/org/apache/rocketmq/common/utils/NameServerAddressUtils.java
@@ -35,7 +35,11 @@ public static String parseInstanceIdFromEndpoint(String endpoint) {
         if (StringUtils.isEmpty(endpoint)) {
             return null;
         }
-        return endpoint.substring(endpoint.lastIndexOf("/") + 1, endpoint.indexOf('.'));
+        int dotIndex = endpoint.indexOf('.');
+        if (dotIndex < 0) {
+            return null;
+        }
+        return endpoint.substring(endpoint.lastIndexOf("/") + 1, dotIndex);
     }
 
     public static String getNameSrvAddrFromNamesrvEndpoint(String nameSrvEndpoint) {
diff --git a/common/src/test/java/org/apache/rocketmq/common/utils/NameServerAddressUtilsTest.java b/common/src/test/java/org/apache/rocketmq/common/utils/NameServerAddressUtilsTest.java
index 38cffdba9dd..7b79d54dc51 100644
--- a/common/src/test/java/org/apache/rocketmq/common/utils/NameServerAddressUtilsTest.java
+++ b/common/src/test/java/org/apache/rocketmq/common/utils/NameServerAddressUtilsTest.java
@@ -45,6 +45,14 @@ public void testParseInstanceIdFromEndpoint() {
             "MQ_INST_123456789_BXXUzaee");
     }
 
+    @Test
+    public void testParseInstanceIdFromEndpointWithoutDot() {
+        // an endpoint without a dot is not an instance endpoint; the utility must
+        // not throw StringIndexOutOfBoundsException on it
+        assertThat(NameServerAddressUtils.parseInstanceIdFromEndpoint("MQ_INST_123456789_BXXUzaee:80")).isNull();
+        assertThat(NameServerAddressUtils.parseInstanceIdFromEndpoint("localhost")).isNull();
+    }
+
     @Test
     public void testGetNameSrvAddrFromNamesrvEndpoint() {
         assertThat(NameServerAddressUtils.getNameSrvAddrFromNamesrvEndpoint(endpoint1))