diff --git a/driver-core/src/main/com/mongodb/ConnectionString.java b/driver-core/src/main/com/mongodb/ConnectionString.java
index f779ab7290..69db84eb07 100644
--- a/driver-core/src/main/com/mongodb/ConnectionString.java
+++ b/driver-core/src/main/com/mongodb/ConnectionString.java
@@ -1209,7 +1209,7 @@ private List<String> parseHosts(final List<String> rawHosts) {
                 }
                 int idx = host.indexOf("]:");
                 if (idx != -1) {
-                    validatePort(host, host.substring(idx + 2));
+                    validatePort(host.substring(idx + 2));
                 }
             } else {
                 int colonCount = countOccurrences(host, ":");
@@ -1218,7 +1218,7 @@ private List<String> parseHosts(final List<String> rawHosts) {
                             + "Reserved characters such as ':' must be escaped according RFC 2396. "
                             + "Any IPv6 address literal must be enclosed in '[' and ']' according to RFC 2732.", host));
                 } else if (colonCount == 1) {
-                    validatePort(host, host.substring(host.indexOf(":") + 1));
+                    validatePort(host.substring(host.indexOf(":") + 1));
                 }
             }
             hosts.add(host);
@@ -1227,19 +1227,17 @@ private List<String> parseHosts(final List<String> rawHosts) {
         return hosts;
     }
 
-    private void validatePort(final String host, final String port) {
-        boolean invalidPort = false;
+    private void validatePort(final String port) {
         try {
             int portInt = Integer.parseInt(port);
             if (portInt <= 0 || portInt > 65535) {
-                invalidPort = true;
+                throw new IllegalArgumentException("The connection string contains an invalid host and port. "
+                        + "The port must be an integer between 0 and 65535.");
             }
         } catch (NumberFormatException e) {
-            invalidPort = true;
-        }
-        if (invalidPort) {
-            throw new IllegalArgumentException(format("The connection string contains an invalid host '%s'. "
-                    + "The port '%s' is not a valid, it must be an integer between 0 and 65535", host, port));
+            throw new IllegalArgumentException("The connection string contains an invalid host and port. "
+                    + "The port contains non-digit characters, it must be an integer between 0 and 65535. "
+                    + "Hint: username and password must be escaped according to RFC 3986.");
         }
     }
 
diff --git a/driver-core/src/test/unit/com/mongodb/ConnectionStringUnitTest.java b/driver-core/src/test/unit/com/mongodb/ConnectionStringUnitTest.java
index bc905c9c6d..539a60ea5d 100644
--- a/driver-core/src/test/unit/com/mongodb/ConnectionStringUnitTest.java
+++ b/driver-core/src/test/unit/com/mongodb/ConnectionStringUnitTest.java
@@ -19,6 +19,7 @@
 import com.mongodb.connection.ServerMonitoringMode;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
 import org.junit.jupiter.params.provider.ValueSource;
 
 import java.io.UnsupportedEncodingException;
@@ -27,6 +28,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -92,4 +94,20 @@ void serverMonitoringMode() {
                         () -> new ConnectionString(DEFAULT_OPTIONS + "serverMonitoringMode=invalid"))
         );
     }
+
+
+    @ParameterizedTest
+    @ValueSource(strings = {"mongodb://foo:bar/@hostname/java?", "mongodb://foo:bar?@hostname/java/",
+                            "mongodb+srv://foo:bar/@hostname/java?", "mongodb+srv://foo:bar?@hostname/java/",
+                            "mongodb://foo:bar/@[::1]:27018", "mongodb://foo:bar?@[::1]:27018",
+                            "mongodb://foo:12345678/@hostname", "mongodb+srv://foo:12345678/@hostname",
+                            "mongodb://foo:12345678/@hostname", "mongodb+srv://foo:12345678/@hostname",
+                            "mongodb://foo:12345678%40hostname", "mongodb+srv://foo:12345678%40hostname",
+                            "mongodb://foo:12345678@bar@hostname", "mongodb+srv://foo:12345678@bar@hostname"
+    })
+    void unescapedPasswordsShouldNotBeLeakedInExceptionMessages(final String input) {
+        IllegalArgumentException exception = assertThrows(IllegalArgumentException.class, () -> new ConnectionString(input));
+        assertFalse(exception.getMessage().contains("bar"));
+        assertFalse(exception.getMessage().contains("12345678"));
+    }
 }