diff --git a/CHANGES.txt b/CHANGES.txt
index f39b7ff06a..fbc2301eac 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,5 @@
 4.0.21
+ * Fix PasswordObfuscator failing to obfuscate certain passwords (CASSANDRA-21113)
  * Fix negative memtable allocator ownership when an update is shadowed by an existing row deletion (CASSANDRA-21469)
  * Consider first token of SSTable when calculating SSTable intersection in LeveledScanner  (CASSANDRA-21369)
  * Remove inFlightEcho entry on ECHO_REQ failure (CASSANDRA-21428)
diff --git a/src/java/org/apache/cassandra/cql3/PasswordObfuscator.java b/src/java/org/apache/cassandra/cql3/PasswordObfuscator.java
index 89962f90d7..f648ccf87f 100644
--- a/src/java/org/apache/cassandra/cql3/PasswordObfuscator.java
+++ b/src/java/org/apache/cassandra/cql3/PasswordObfuscator.java
@@ -18,6 +18,8 @@
 
 package org.apache.cassandra.cql3;
 
+import java.util.regex.Pattern;
+
 import com.google.common.base.Optional;
 
 import org.apache.cassandra.auth.PasswordAuthenticator;
@@ -65,7 +67,11 @@ public class PasswordObfuscator
         if (!pass.isPresent() || pass.get().isEmpty())
             return query;
 
-        // match new line, case insensitive (?si), and PASSWORD_TOKEN up to the actual password greedy. Group that and replace the password
-        return query.replaceAll("((?si)"+ PASSWORD_TOKEN + ".+?)" + pass.get(), "$1" + PasswordObfuscator.OBFUSCATION_TOKEN);
+        // CQL-escape the password, the password in RoleOptions is unescaped, but the query contains the escaped form.
+        String escapedPassword = pass.get().replace("'", "''");
+
+        // Use Pattern.quote() to safely handle all special regex characters.
+        String pattern = "((?si)" + PASSWORD_TOKEN + ".+?)" + Pattern.quote(escapedPassword);
+        return query.replaceAll(pattern, "$1" + OBFUSCATION_TOKEN);
     }
 }
diff --git a/test/unit/org/apache/cassandra/cql3/PasswordObfuscatorTest.java b/test/unit/org/apache/cassandra/cql3/PasswordObfuscatorTest.java
index 09a366e49c..f1bebae139 100644
--- a/test/unit/org/apache/cassandra/cql3/PasswordObfuscatorTest.java
+++ b/test/unit/org/apache/cassandra/cql3/PasswordObfuscatorTest.java
@@ -18,24 +18,31 @@
 
 package org.apache.cassandra.cql3;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import org.apache.cassandra.auth.IRoleManager;
 import org.apache.cassandra.auth.RoleOptions;
 
 import static org.apache.cassandra.cql3.PasswordObfuscator.*;
 import static java.lang.String.format;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 
 public class PasswordObfuscatorTest
 {
     private static final RoleOptions opts = new RoleOptions();
     private static final String optsPassword = "testpassword";
+    public static final int ASCII_START = 32;
+    public static final int ASCII_END = 126;
 
     @BeforeClass
     public static void startup()
     {
-        opts.setOption(org.apache.cassandra.auth.IRoleManager.Option.PASSWORD, "testpassword");
+        opts.setOption(org.apache.cassandra.auth.IRoleManager.Option.PASSWORD, optsPassword);
     }
 
     @Test
@@ -237,4 +244,121 @@ public class PasswordObfuscatorTest
                                       "APPLY BATCH;", optsPassword, optsPassword),
                                opts));
     }
+
+    /**
+     * Tests that passwords containing the literal string \E are properly obfuscated.
+     * <p>
+     * The \E sequence is special in Java regex as it ends a \Q...\E quoted block.
+     * If inline \Q...\E quoting is used instead of Pattern.quote(), passwords containing
+     * \E will break the regex pattern and cause either an exception or failed obfuscation.
+     */
+    @Test
+    public void testPasswordWithRegexEndQuote()
+    {
+        // \E in the middle
+        assertPasswordObfuscated("secret\\Epassword");
+
+        // \E at the start
+        assertPasswordObfuscated("\\Esecretpassword");
+
+        // \E at the end
+        assertPasswordObfuscated("secretpassword\\E");
+
+        // \E followed by regex special char +
+        assertPasswordObfuscated("secret\\E+password");
+
+        // Multiple \E sequences
+        assertPasswordObfuscated("sec\\Eret\\Epass");
+    }
+
+    /**
+     * Helper method to test that a password is properly obfuscated in a CREATE ROLE statement.
+     *
+     * @param password the password to test (unescaped, as stored in RoleOptions)
+     */
+    private void assertPasswordObfuscated(String password)
+    {
+        RoleOptions roleOpts = new RoleOptions();
+        roleOpts.setOption(IRoleManager.Option.PASSWORD, password);
+
+        // Escape single quotes for CQL query string
+        String escapedPassword = password.replace("'", "''");
+        String query = format("CREATE ROLE role1 WITH PASSWORD = '%s'", escapedPassword);
+        String expected = format("CREATE ROLE role1 WITH PASSWORD = '%s'", OBFUSCATION_TOKEN);
+
+        assertEquals("Password should be obfuscated: " + password, expected, obfuscate(query, roleOpts));
+    }
+
+    /**
+     * Tests that passwords containing each printable special character (outside a-z, A-Z, 0-9)
+     * are properly obfuscated by PasswordObfuscator.
+     * <p>
+     * This test iterates through all printable ASCII special characters (32-126, excluding
+     * alphanumeric) and tests each character at three positions: start, middle, and end of
+     * the password. Any failures are collected and reported at the end.
+     */
+    @Test
+    public void testAllPrintableSpecialCharactersObfuscation()
+    {
+        List<String> failures = new ArrayList<>();
+
+        for (char c = ASCII_START; c <= ASCII_END; c++)
+        {
+            // Skip alphanumeric characters
+            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'))
+                continue;
+
+            // Test character at start, middle, and end of password
+            String[] passwords = {
+                c + "password",        // at start
+                "pass" + c + "word",   // in middle
+                "password" + c         // at end
+            };
+
+            for (String password : passwords)
+            {
+                String escapedPassword = password.replace("'", "''");
+                String query = format("CREATE ROLE role1 WITH PASSWORD = '%s'", escapedPassword);
+                String expected = format("CREATE ROLE role1 WITH PASSWORD = '%s'", OBFUSCATION_TOKEN);
+
+                RoleOptions testOpts = new RoleOptions();
+                testOpts.setOption(IRoleManager.Option.PASSWORD, password);
+
+                try
+                {
+                    String result = obfuscate(query, testOpts);
+
+                    if (!expected.equals(result))
+                    {
+                        if (result.contains(escapedPassword) || result.contains(password))
+                        {
+                            failures.add(format("Password '%s': PASSWORD LEAKED - Result: %s",
+                                                password, result));
+                        }
+                        else
+                        {
+                            failures.add(format("Password '%s': Unexpected result - Expected: %s, Got: %s",
+                                                password, expected, result));
+                        }
+                    }
+                }
+                catch (Exception e)
+                {
+                    failures.add(format("Password '%s': Exception thrown - %s: %s",
+                                        password, e.getClass().getSimpleName(), e.getMessage()));
+                }
+            }
+        }
+
+        if (!failures.isEmpty())
+        {
+            StringBuilder sb = new StringBuilder();
+            sb.append(format("%d password(s) with special characters failed obfuscation:\n", failures.size()));
+            for (String failure : failures)
+            {
+                sb.append("  - ").append(failure).append("\n");
+            }
+            fail(sb.toString());
+        }
+    }
 }