From e44df496cec4f5b5420134a8621e9266859e2536 Mon Sep 17 00:00:00 2001
From: jimmychakkalakal <47317106+jimmychakkalakal@users.noreply.github.com>
Date: Thu, 18 Jun 2026 15:04:12 +0000
Subject: [PATCH] Reject redirect URIs containing pre-loaded OIDC response parameters (#49959)

---
 src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java b/src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java
index 51432b1..d367deb 100644
--- a/src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java
+++ b/src/main/java/org/keycloak/protocol/cas/utils/RedirectUtils.java
@@ -23,11 +23,14 @@
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Locale;
 import java.util.Set;
 import java.util.TreeSet;
 import java.util.regex.Pattern;
 
+import org.keycloak.OAuth2Constants;
 import org.keycloak.common.util.KeycloakUriBuilder;
+import org.keycloak.common.util.MultivaluedHashMap;
 import org.keycloak.common.util.UriUtils;
 import org.keycloak.models.ClientModel;
 import org.keycloak.models.Constants;
@@ -46,6 +49,22 @@
 
     public static final Set<String> LOOPBACK_INTERFACES = new HashSet<>(Arrays.asList("localhost", "127.0.0.1", "[::1]"));
 
+    private static final Set<String> FORBIDDEN_OIDC_PARAMS = Set.of(
+                                                                     OAuth2Constants.CODE,
+                                                                     OAuth2Constants.ID_TOKEN,
+                                                                     OAuth2Constants.ACCESS_TOKEN,
+                                                                     OAuth2Constants.TOKEN_TYPE,
+                                                                     OAuth2Constants.EXPIRES_IN,
+                                                                     OAuth2Constants.STATE,
+                                                                     OAuth2Constants.ISSUER,
+                                                                     OAuth2Constants.ERROR,
+                                                                     OAuth2Constants.ERROR_DESCRIPTION,
+                                                                     OAuth2Constants.SESSION_STATE,
+                                                                     OAuth2Constants.RESPONSE,
+                                                                     Constants.KC_ACTION,
+                                                                     Constants.KC_ACTION_STATUS
+                                                                   );
+
     private static final Logger logger = Logger.getLogger(RedirectUtils.class);
 
     public static String verifyRedirectUri(KeycloakSession session, String redirectUri, ClientModel client) {
@@ -95,6 +114,11 @@
                 return null;
             }
 
+            // Check for HTTP Parameter Pollution - forbidden OIDC response parameters in redirect URI
+            if (containsForbiddenOidcParameters(originalRedirect)){
+                return null;
+            }
+
             // check if the passed URI allows wildcards
             boolean allowWildcards = areWildcardsAllowed(originalRedirect);
 
@@ -135,6 +159,24 @@
         }
     }
 
+    private static boolean containsForbiddenOidcParameters(URI originalRedirect) {
+        String query = originalRedirect.getRawQuery();
+        if (query != null && !query.isEmpty()) {
+            MultivaluedHashMap<String, String> params =UriUtils.decodeQueryString(query);
+            for (String paramName : params.keySet()) {
+                if (FORBIDDEN_OIDC_PARAMS.contains(paramName.toLowerCase(Locale.ROOT))) {
+                    logger.warnf("Redirect URI rejected: contains forbidden OIDC parameter '%s' in query string: scheme=%s, host=%s, path=%s",
+                            paramName,
+                            originalRedirect.getScheme(),
+                            originalRedirect.getHost(),
+                            originalRedirect.getPath());
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     private static URI toUri(String redirectUri) {
         URI uri = null;
         if (redirectUri != null) {

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