diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java b/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java
index 4e08336dd68..39a70aeb8f1 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockCookie.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockCookie.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.
@@ -175,7 +175,8 @@ public class MockCookie extends Cookie {
 				cookie.setComment(extractAttributeValue(attribute, setCookieHeader));
 			}
 			else if (!attribute.isEmpty()) {
-				cookie.setAttribute(attribute, extractOptionalAttributeValue(attribute, setCookieHeader));
+				String[] nameAndValue = extractOptionalAttributeNameAndValue(attribute, setCookieHeader);
+				cookie.setAttribute(nameAndValue[0], nameAndValue[1]);
 			}
 		}
 		return cookie;
@@ -188,9 +189,9 @@ public class MockCookie extends Cookie {
 		return nameAndValue[1];
 	}
 
-	private static String extractOptionalAttributeValue(String attribute, String header) {
+	private static String[] extractOptionalAttributeNameAndValue(String attribute, String header) {
 		String[] nameAndValue = attribute.split("=");
-		return nameAndValue.length == 2 ? nameAndValue[1] : "";
+		return (nameAndValue.length == 2 ? nameAndValue : new String[] {attribute, ""});
 	}
 
 	@Override
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java
index e078b380940..eba5998acac 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockCookieTests.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.
@@ -68,8 +68,8 @@ class MockCookieTests {
 		assertCookie(cookie, "SESSION", "123");
 	}
 
-	@SuppressWarnings("removal")
 	@Test
+	@SuppressWarnings("removal")
 	void parseHeaderWithAttributes() {
 		MockCookie cookie = MockCookie.parse("SESSION=123; Domain=example.com; Max-Age=60; " +
 				"Expires=Tue, 8 Oct 2019 19:50:00 GMT; Path=/; Secure; HttpOnly; Partitioned; SameSite=Lax");
@@ -87,6 +87,19 @@ class MockCookieTests {
 		assertThat(cookie.getComment()).isNull();
 	}
 
+	@Test  // gh-34575
+	void parseHeaderWithOptionalAttributes() {
+		MockCookie cookie = MockCookie.parse("SESSION=123; HttpOnly; Version=1; Partitioned; Secure");
+
+		assertCookie(cookie, "SESSION", "123");
+		assertThat(cookie.isHttpOnly()).isTrue();
+		assertThat(cookie.getSecure()).isTrue();
+		assertThat(cookie.isPartitioned()).isTrue();
+		assertThat(cookie.getAttribute("Partitioned")).isEmpty();
+		assertThat(cookie.getAttribute("Version")).isEqualTo("1");
+		assertThat(cookie.getAttribute("BOGUS")).isNull();
+	}
+
 	@ParameterizedTest
 	@ValueSource(strings = {"0", "bogus"})
 	void parseHeaderWithInvalidExpiresAttribute(String expiresValue) {
@@ -209,10 +222,13 @@ class MockCookieTests {
 	void setPartitioned() {
 		MockCookie cookie = new MockCookie("SESSION", "123");
 		assertThat(cookie.isPartitioned()).isFalse();
+		assertThat(cookie.getAttribute("Partitioned")).isNull();
 		cookie.setPartitioned(true);
 		assertThat(cookie.isPartitioned()).isTrue();
+		assertThat(cookie.getAttribute("Partitioned")).isEmpty();
 		cookie.setPartitioned(false);
 		assertThat(cookie.isPartitioned()).isFalse();
+		assertThat(cookie.getAttribute("Partitioned")).isNull();
 	}
 
 }
diff --git a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockCookie.java b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockCookie.java
index 73053568d37..512a145d12f 100644
--- a/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockCookie.java
+++ b/spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockCookie.java
@@ -175,7 +175,8 @@ public class MockCookie extends Cookie {
 				cookie.setComment(extractAttributeValue(attribute, setCookieHeader));
 			}
 			else if (!attribute.isEmpty()) {
-				cookie.setAttribute(attribute, extractOptionalAttributeValue(attribute, setCookieHeader));
+				String[] nameAndValue = extractOptionalAttributeNameAndValue(attribute, setCookieHeader);
+				cookie.setAttribute(nameAndValue[0], nameAndValue[1]);
 			}
 		}
 		return cookie;
@@ -188,9 +189,9 @@ public class MockCookie extends Cookie {
 		return nameAndValue[1];
 	}
 
-	private static String extractOptionalAttributeValue(String attribute, String header) {
+	private static String[] extractOptionalAttributeNameAndValue(String attribute, String header) {
 		String[] nameAndValue = attribute.split("=");
-		return nameAndValue.length == 2 ? nameAndValue[1] : "";
+		return (nameAndValue.length == 2 ? nameAndValue : new String[] {attribute, ""});
 	}
 
 	@Override