diff --git a/sandbox/libs/authn/src/main/java/org/opensearch/authn/AuthenticationTokenHandler.java b/sandbox/libs/authn/src/main/java/org/opensearch/authn/AuthenticationTokenHandler.java
index 12840c3ee8006..4a4cb6f061780 100644
--- a/sandbox/libs/authn/src/main/java/org/opensearch/authn/AuthenticationTokenHandler.java
+++ b/sandbox/libs/authn/src/main/java/org/opensearch/authn/AuthenticationTokenHandler.java
@@ -48,13 +48,29 @@ private static AuthenticationToken handleBasicAuth(final BasicAuthToken token) {
         final byte[] decodedAuthHeader = Base64.getDecoder().decode(token.getHeaderValue().substring("Basic".length()).trim());
         String decodedHeader = new String(decodedAuthHeader, StandardCharsets.UTF_8);
 
-        final String[] decodedUserNamePassword = decodedHeader.split(":");
+        final int firstColonIndex = decodedHeader.indexOf(':');
 
-        // Malformed AuthHeader strings
-        if (decodedUserNamePassword.length != 2) return null;
+        String username = null;
+        String password = null;
 
-        logger.info("Logging in as: " + decodedUserNamePassword[0]);
+        if (firstColonIndex > 0) {
+            username = decodedHeader.substring(0, firstColonIndex);
 
-        return new UsernamePasswordToken(decodedUserNamePassword[0], decodedUserNamePassword[1]);
+            if (decodedHeader.length() - 1 != firstColonIndex) {
+                password = decodedHeader.substring(firstColonIndex + 1);
+            } else {
+                // blank password
+                password = "";
+            }
+        }
+
+        if (username == null || password == null) {
+            logger.warn("Invalid 'Authorization' header, send 401 and 'WWW-Authenticate Basic'");
+            return null;
+        }
+
+        logger.info("Logging in as: " + username);
+
+        return new UsernamePasswordToken(username, password);
     }
 }
diff --git a/sandbox/libs/authn/src/main/resources/example/example_internal_users.yml b/sandbox/libs/authn/src/main/resources/example/example_internal_users.yml
index 96453a6aed8f5..0c66535211737 100644
--- a/sandbox/libs/authn/src/main/resources/example/example_internal_users.yml
+++ b/sandbox/libs/authn/src/main/resources/example/example_internal_users.yml
@@ -30,3 +30,7 @@ readall:
 
 snapshotrestore:
   hash: "$2y$12$DpwmetHKwgYnorbgdvORCenv4NAK8cPUg8AI6pxLCuWf/ALc0.v7W"
+
+# Two semi-colon password
+test:
+  hash: "$2y$12$fG1vNbK3X73j9eujLfh6We43fbKdy8O8RP5tGnLjg/CWMot48kAwO"    # te:st
diff --git a/sandbox/libs/authn/src/test/java/org/opensearch/authn/AuthenticationTokenHandlerTests.java b/sandbox/libs/authn/src/test/java/org/opensearch/authn/AuthenticationTokenHandlerTests.java
index ca67b7f0b2633..03dcf6b26a53f 100644
--- a/sandbox/libs/authn/src/test/java/org/opensearch/authn/AuthenticationTokenHandlerTests.java
+++ b/sandbox/libs/authn/src/test/java/org/opensearch/authn/AuthenticationTokenHandlerTests.java
@@ -11,6 +11,7 @@
 import org.opensearch.authn.tokens.BasicAuthToken;
 import org.opensearch.test.OpenSearchTestCase;
 
+import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.nullValue;
 
@@ -26,6 +27,22 @@ public void testShouldExtractBasicAuthTokenSuccessfully() {
         UsernamePasswordToken usernamePasswordToken = (UsernamePasswordToken) AuthenticationTokenHandler.extractShiroAuthToken(authToken);
 
         MatcherAssert.assertThat(usernamePasswordToken, notNullValue());
+        MatcherAssert.assertThat(usernamePasswordToken.getUsername(), equalTo("admin"));
+        MatcherAssert.assertThat(new String(usernamePasswordToken.getPassword()), equalTo("admin"));
+    }
+
+    public void testShouldExtractBasicAuthTokenSuccessfully_twoSemiColonPassword() {
+
+        // The auth header that is part of the request
+        String authHeader = "Basic dGVzdDp0ZTpzdA=="; // test:te:st
+
+        AuthenticationToken authToken = new BasicAuthToken(authHeader);
+
+        UsernamePasswordToken usernamePasswordToken = (UsernamePasswordToken) AuthenticationTokenHandler.extractShiroAuthToken(authToken);
+
+        MatcherAssert.assertThat(usernamePasswordToken, notNullValue());
+        MatcherAssert.assertThat(usernamePasswordToken.getUsername(), equalTo("test"));
+        MatcherAssert.assertThat(new String(usernamePasswordToken.getPassword()), equalTo("te:st"));
     }
 
     public void testShouldReturnNullWhenExtractingInvalidToken() {
diff --git a/sandbox/libs/authn/src/test/java/org/opensearch/authn/type/BasicAuthenticationTests.java b/sandbox/libs/authn/src/test/java/org/opensearch/authn/type/BasicAuthenticationTests.java
index 220f66a55885b..8d71686146f52 100644
--- a/sandbox/libs/authn/src/test/java/org/opensearch/authn/type/BasicAuthenticationTests.java
+++ b/sandbox/libs/authn/src/test/java/org/opensearch/authn/type/BasicAuthenticationTests.java
@@ -32,6 +32,20 @@ public void testClusterHealthWithValidAuthenticationHeader() throws IOException
 
     }
 
+    public void testClusterHealthWithValidAuthenticationHeader_twoSemiColonPassword() throws IOException {
+        Request request = new Request("GET", "/_cluster/health");
+        RequestOptions options = RequestOptions.DEFAULT.toBuilder().addHeader("Authorization", "Basic dGVzdDp0ZTpzdA==").build(); // test:te:st
+        request.setOptions(options);
+        Response response = client().performRequest(request);
+
+        assertOK(response);
+
+        // Standard cluster health response
+        MatcherAssert.assertThat(entityAsMap(response).size(), equalTo(17));
+        MatcherAssert.assertThat(entityAsMap(response).get("status"), equalTo("green"));
+
+    }
+
     public void testClusterHealthWithNoHeader() throws IOException {
         Request request = new Request("GET", "/_cluster/health");
         RequestOptions options = RequestOptions.DEFAULT.toBuilder().build(); // admin:admin
@@ -65,8 +79,7 @@ public void testClusterHealthWithInvalidAuthenticationHeader() throws IOExceptio
 
     public void testClusterHealthWithCorruptAuthenticationHeader() throws IOException {
         Request request = new Request("GET", "/_cluster/health");
-        RequestOptions options = RequestOptions.DEFAULT.toBuilder().addHeader("Authorization", "Basic bleh").build(); // marvin:galaxy
-        request.setOptions(options);
+        RequestOptions options = RequestOptions.DEFAULT.toBuilder().addHeader("Authorization", "Basic bleh").build();
         try {
             client().performRequest(request);
         } catch (ResponseException e) {