diff --git a/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java b/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
index 359a7d48809..229054b0239 100644
--- a/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
+++ b/config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java
@@ -191,6 +191,12 @@
 import org.springframework.security.web.firewall.RequestRejectedException;
 import org.springframework.security.web.server.firewall.ServerExchangeRejectedException;
 import org.springframework.security.web.session.HttpSessionCreatedEvent;
+import org.springframework.security.web.webauthn.api.Bytes;
+import org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity;
+import org.springframework.security.web.webauthn.api.PublicKeyCredentialUserEntity;
+import org.springframework.security.web.webauthn.api.TestBytes;
+import org.springframework.security.web.webauthn.api.TestPublicKeyCredentialUserEntity;
+import org.springframework.security.web.webauthn.authentication.WebAuthnAuthentication;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -508,6 +514,20 @@ class SpringSecurityCoreVersionSerializableTests {
 				(r) -> new AuthenticationSwitchUserEvent(authentication, user));
 		generatorByClassName.put(HttpSessionCreatedEvent.class,
 				(r) -> new HttpSessionCreatedEvent(new MockHttpSession()));
+
+		// webauthn
+		generatorByClassName.put(Bytes.class, (r) -> TestBytes.getInstance());
+		generatorByClassName.put(ImmutablePublicKeyCredentialUserEntity.class,
+				(r) -> TestPublicKeyCredentialUserEntity.userEntity().id(TestBytes.getInstance()).build());
+		generatorByClassName.put(WebAuthnAuthentication.class, (r) -> {
+			PublicKeyCredentialUserEntity userEntity = TestPublicKeyCredentialUserEntity.userEntity()
+				.id(TestBytes.getInstance())
+				.build();
+			List<GrantedAuthority> authorities = AuthorityUtils.createAuthorityList("ROLE_USER");
+			WebAuthnAuthentication webAuthnAuthentication = new WebAuthnAuthentication(userEntity, authorities);
+			webAuthnAuthentication.setDetails(details);
+			return webAuthnAuthentication;
+		});
 	}
 
 	@ParameterizedTest
diff --git a/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.Bytes.serialized b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.Bytes.serialized
new file mode 100644
index 00000000000..483bef50163
Binary files /dev/null and b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.Bytes.serialized differ
diff --git a/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity.serialized b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity.serialized
new file mode 100644
index 00000000000..eb662f4843a
Binary files /dev/null and b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity.serialized differ
diff --git a/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.authentication.WebAuthnAuthentication.serialized b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.authentication.WebAuthnAuthentication.serialized
new file mode 100644
index 00000000000..a5baa210e66
Binary files /dev/null and b/config/src/test/resources/serialized/6.4.x/org.springframework.security.web.webauthn.authentication.WebAuthnAuthentication.serialized differ
diff --git a/web/src/main/java/org/springframework/security/web/webauthn/api/Bytes.java b/web/src/main/java/org/springframework/security/web/webauthn/api/Bytes.java
index 6fbcc3596c6..6c96a11efd8 100644
--- a/web/src/main/java/org/springframework/security/web/webauthn/api/Bytes.java
+++ b/web/src/main/java/org/springframework/security/web/webauthn/api/Bytes.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.web.webauthn.api;
 
+import java.io.Serial;
+import java.io.Serializable;
 import java.security.SecureRandom;
 import java.util.Arrays;
 import java.util.Base64;
@@ -28,7 +30,10 @@
  * @author Rob Winch
  * @since 6.4
  */
-public final class Bytes {
+public final class Bytes implements Serializable {
+
+	@Serial
+	private static final long serialVersionUID = -3278138671365709777L;
 
 	private static final SecureRandom RANDOM = new SecureRandom();
 
diff --git a/web/src/main/java/org/springframework/security/web/webauthn/api/ImmutablePublicKeyCredentialUserEntity.java b/web/src/main/java/org/springframework/security/web/webauthn/api/ImmutablePublicKeyCredentialUserEntity.java
index 3b2fe5adfa0..a383967f7db 100644
--- a/web/src/main/java/org/springframework/security/web/webauthn/api/ImmutablePublicKeyCredentialUserEntity.java
+++ b/web/src/main/java/org/springframework/security/web/webauthn/api/ImmutablePublicKeyCredentialUserEntity.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.web.webauthn.api;
 
+import java.io.Serial;
+
 /**
  * <a href=
  * "https://www.w3.org/TR/webauthn-3/#dictdef-publickeycredentialuserentity">PublicKeyCredentialUserEntity</a>
@@ -28,6 +30,9 @@
  */
 public final class ImmutablePublicKeyCredentialUserEntity implements PublicKeyCredentialUserEntity {
 
+	@Serial
+	private static final long serialVersionUID = -3438693960347279759L;
+
 	/**
 	 * When inherited by PublicKeyCredentialUserEntity, it is a human-palatable identifier
 	 * for a user account. It is intended only for display, i.e., aiding the user in
diff --git a/web/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java b/web/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
index fd95a24c715..b3d1b9a86ac 100644
--- a/web/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
+++ b/web/src/main/java/org/springframework/security/web/webauthn/api/PublicKeyCredentialUserEntity.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.web.webauthn.api;
 
+import java.io.Serializable;
+
 /**
  * <a href=
  * "https://www.w3.org/TR/webauthn-3/#dictdef-publickeycredentialuserentity">PublicKeyCredentialUserEntity</a>
@@ -27,7 +29,7 @@
  * @since 6.4
  * @see org.springframework.security.web.webauthn.management.WebAuthnRelyingPartyOperations#authenticate(org.springframework.security.web.webauthn.management.RelyingPartyAuthenticationRequest)
  */
-public interface PublicKeyCredentialUserEntity {
+public interface PublicKeyCredentialUserEntity extends Serializable {
 
 	/**
 	 * The <a href=
diff --git a/web/src/main/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthentication.java b/web/src/main/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthentication.java
index 8964e0b13e0..51be1e76f22 100644
--- a/web/src/main/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthentication.java
+++ b/web/src/main/java/org/springframework/security/web/webauthn/authentication/WebAuthnAuthentication.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.security.web.webauthn.authentication;
 
+import java.io.Serial;
 import java.util.Collection;
 
 import org.springframework.security.authentication.AbstractAuthenticationToken;
@@ -33,6 +34,9 @@
  */
 public class WebAuthnAuthentication extends AbstractAuthenticationToken {
 
+	@Serial
+	private static final long serialVersionUID = -4879907158750659197L;
+
 	private final PublicKeyCredentialUserEntity principal;
 
 	public WebAuthnAuthentication(PublicKeyCredentialUserEntity principal,
diff --git a/web/src/test/java/org/springframework/security/web/webauthn/api/TestBytes.java b/web/src/test/java/org/springframework/security/web/webauthn/api/TestBytes.java
new file mode 100644
index 00000000000..433eadc7068
--- /dev/null
+++ b/web/src/test/java/org/springframework/security/web/webauthn/api/TestBytes.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright 2002-2025 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.security.web.webauthn.api;
+
+public final class TestBytes {
+
+	private static final Bytes INSTANCE = Bytes.random();
+
+	public static Bytes getInstance() {
+
+		return INSTANCE;
+	}
+
+	private TestBytes() {
+	}
+
+}