Kerberos Authentication Bypass in Keycloak

Executive Summary

This vulnerability is in Keycloak's Kerberos federation provider. When Kerberos password authentication is used without SPNEGO, Keycloak fails to verify the Key Distribution Center (KDC) by not requesting a server ticket. This allows an attacker on the same network to spoof the KDC and bypass authentication entirely, potentially gaining unauthorized access to user accounts.

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Detection Guidance

Monitor network traffic for unauthorized Kerberos responses or spoofed KDC communications. Check Keycloak logs for failed authentication attempts or unexpected Kerberos ticket requests. Use tools like Wireshark to inspect Kerberos traffic for anomalies in server ticket requests.

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Impact Analysis

An attacker could impersonate any user, bypass authentication, and gain unauthorized access to sensitive data or administrative functions. The attack requires being on the same network and can be executed without needing special privileges or user interaction.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. It undermines authentication controls, potentially resulting in non-compliance with data protection regulations.

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Mitigation Strategies

Disable Kerberos password authentication without SPNEGO in Keycloak. Ensure SPNEGO is enabled for Kerberos authentication. Monitor network for ARP, DNS, or DHCP spoofing attempts. Apply patches or updates from Keycloak once available.

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