diff --git a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/CodeVerifierAuthenticator.java b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/CodeVerifierAuthenticator.java
index a5664ee1..d3d9f3db 100644
--- a/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/CodeVerifierAuthenticator.java
+++ b/oauth2-authorization-server/src/main/java/org/springframework/security/oauth2/server/authorization/authentication/CodeVerifierAuthenticator.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2023 the original author or authors.
+ * Copyright 2020-2024 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.
@@ -95,8 +95,10 @@ final class CodeVerifierAuthenticator {
 
 		String codeChallenge = (String) authorizationRequest.getAdditionalParameters()
 				.get(PkceParameterNames.CODE_CHALLENGE);
+		String codeVerifier = (String) parameters.get(PkceParameterNames.CODE_VERIFIER);
 		if (!StringUtils.hasText(codeChallenge)) {
-			if (registeredClient.getClientSettings().isRequireProofKey()) {
+			if (registeredClient.getClientSettings().isRequireProofKey() ||
+					StringUtils.hasText(codeVerifier)) {
 				if (this.logger.isDebugEnabled()) {
 					this.logger.debug(LogMessage.format("Invalid request: code_challenge is required" +
 							" for registered client '%s'", registeredClient.getId()));
@@ -116,7 +118,6 @@ final class CodeVerifierAuthenticator {
 
 		String codeChallengeMethod = (String) authorizationRequest.getAdditionalParameters()
 				.get(PkceParameterNames.CODE_CHALLENGE_METHOD);
-		String codeVerifier = (String) parameters.get(PkceParameterNames.CODE_VERIFIER);
 		if (!codeVerifierValid(codeVerifier, codeChallenge, codeChallengeMethod)) {
 			if (this.logger.isDebugEnabled()) {
 				this.logger.debug(LogMessage.format("Invalid request: code_verifier is missing or invalid" +
diff --git a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/config/annotation/web/configurers/OAuth2AuthorizationCodeGrantTests.java b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/config/annotation/web/configurers/OAuth2AuthorizationCodeGrantTests.java
index 15063311..23bf9409 100644
--- a/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/config/annotation/web/configurers/OAuth2AuthorizationCodeGrantTests.java
+++ b/oauth2-authorization-server/src/test/java/org/springframework/security/oauth2/server/authorization/config/annotation/web/configurers/OAuth2AuthorizationCodeGrantTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2023 the original author or authors.
+ * Copyright 2020-2024 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.
@@ -540,6 +540,35 @@ public class OAuth2AuthorizationCodeGrantTests {
 		assertThat(redirectedUrl).isEqualTo(expectedRedirectUri);
 	}
 
+	@Test
+	public void requestWhenConfidentialClientWithPkceAndMissingCodeChallengeButCodeVerifierProvidedThenBadRequest() throws Exception {
+		this.spring.register(AuthorizationServerConfiguration.class).autowire();
+
+		RegisteredClient registeredClient = TestRegisteredClients.registeredClient().build();
+		this.registeredClientRepository.save(registeredClient);
+
+		MultiValueMap<String, String> authorizationRequestParameters = getAuthorizationRequestParameters(registeredClient);
+		MvcResult mvcResult = this.mvc.perform(get(DEFAULT_AUTHORIZATION_ENDPOINT_URI)
+						.queryParams(authorizationRequestParameters)
+						.with(user("user")))
+				.andExpect(status().is3xxRedirection())
+				.andReturn();
+		String redirectedUrl = mvcResult.getResponse().getRedirectedUrl();
+		String expectedRedirectUri = authorizationRequestParameters.getFirst(OAuth2ParameterNames.REDIRECT_URI);
+		assertThat(redirectedUrl).matches(expectedRedirectUri + "\\?code=.{15,}&state=" + STATE_URL_ENCODED);
+
+		String authorizationCode = extractParameterFromRedirectUri(redirectedUrl, "code");
+		OAuth2Authorization authorizationCodeAuthorization = this.authorizationService.findByToken(authorizationCode, AUTHORIZATION_CODE_TOKEN_TYPE);
+		assertThat(authorizationCodeAuthorization).isNotNull();
+		assertThat(authorizationCodeAuthorization.getAuthorizationGrantType()).isEqualTo(AuthorizationGrantType.AUTHORIZATION_CODE);
+
+		this.mvc.perform(post(DEFAULT_TOKEN_ENDPOINT_URI)
+				.params(getTokenRequestParameters(registeredClient, authorizationCodeAuthorization))
+				.param(PkceParameterNames.CODE_VERIFIER, S256_CODE_VERIFIER)
+				.header(HttpHeaders.AUTHORIZATION, getAuthorizationHeader(registeredClient)))
+				.andExpect(status().isBadRequest());
+	}
+
 	@Test
 	public void requestWhenCustomTokenGeneratorThenUsed() throws Exception {
 		this.spring.register(AuthorizationServerConfigurationWithTokenGenerator.class).autowire();