diff --git a/CHANGES.txt b/CHANGES.txt
index d848eff418..af185cfec1 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -6,6 +6,7 @@
  * Duplicate the buffer before passing it to analyser in SASI operation (CASSANDRA-13512)
  * Properly evict pstmts from prepared statements cache (CASSANDRA-13641)
 Merged from 3.0:
+ * Better tolerate improperly formatted bcrypt hashes (CASSANDRA-13626)
  * Fix race condition in read command serialization (CASSANDRA-13363)
  * Fix AssertionError in short read protection (CASSANDRA-13747)
  * Don't skip corrupted sstables on startup (CASSANDRA-13620)
diff --git a/src/java/org/apache/cassandra/auth/PasswordAuthenticator.java b/src/java/org/apache/cassandra/auth/PasswordAuthenticator.java
index 4b667aed1e..54f798552b 100644
--- a/src/java/org/apache/cassandra/auth/PasswordAuthenticator.java
+++ b/src/java/org/apache/cassandra/auth/PasswordAuthenticator.java
@@ -82,12 +82,26 @@ public class PasswordAuthenticator implements IAuthenticator
         return true;
     }
 
+    protected static boolean checkpw(String password, String hash)
+    {
+        try
+        {
+            return BCrypt.checkpw(password, hash);
+        }
+        catch (Exception e)
+        {
+            // Improperly formatted hashes may cause BCrypt.checkpw to throw, so trap any other exception as a failure
+            logger.warn("Error: invalid password hash encountered, rejecting user", e);
+            return false;
+        }
+    }
+
     private AuthenticatedUser authenticate(String username, String password) throws AuthenticationException
     {
         try
         {
             String hash = cache.get(username);
-            if (!BCrypt.checkpw(password, hash))
+            if (!checkpw(password, hash))
                 throw new AuthenticationException(String.format("Provided username %s and/or password are incorrect", username));
 
             return new AuthenticatedUser(username);
diff --git a/test/unit/org/apache/cassandra/auth/PasswordAuthenticatorTest.java b/test/unit/org/apache/cassandra/auth/PasswordAuthenticatorTest.java
new file mode 100644
index 0000000000..37763d74de
--- /dev/null
+++ b/test/unit/org/apache/cassandra/auth/PasswordAuthenticatorTest.java
@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.cassandra.auth;
+
+
+import org.junit.Test;
+
+import static org.apache.cassandra.auth.CassandraRoleManager.*;
+import static org.apache.cassandra.auth.PasswordAuthenticator.*;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mindrot.jbcrypt.BCrypt.hashpw;
+import static org.mindrot.jbcrypt.BCrypt.gensalt;
+
+public class PasswordAuthenticatorTest
+{
+    @Test
+    public void testCheckpw() throws Exception
+    {
+        // Valid and correct
+        assertTrue(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw(DEFAULT_SUPERUSER_PASSWORD, gensalt(getGensaltLogRounds()))));
+        assertTrue(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw(DEFAULT_SUPERUSER_PASSWORD, gensalt(4))));
+        assertTrue(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw(DEFAULT_SUPERUSER_PASSWORD, gensalt(31))));
+
+        // Valid but incorrect hashes
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw("incorrect0", gensalt(4))));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw("incorrect1", gensalt(10))));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, hashpw("incorrect2", gensalt(31))));
+
+        // Invalid hash values, the jBCrypt library implementation
+        // throws an exception which we catch and treat as a failure
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, ""));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "0"));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD,
+                            "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"));
+
+        // Format is structurally right, but actually invalid
+        // bad salt version
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$5x$10$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        // invalid number of rounds, multiple salt versions but it's the rounds that are incorrect
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2$02$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2a$02$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2$99$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2a$99$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        // unpadded rounds
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2$6$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+        assertFalse(checkpw(DEFAULT_SUPERUSER_PASSWORD, "$2a$6$abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUVWXYZ01234"));
+    }
+}
\ No newline at end of file