CVE-2023-6787 in Keycloak
Summary
by MITRE • 04/25/2024
A flaw was found in Keycloak that occurs from an error in the re-authentication mechanism within org.keycloak.authentication. This flaw allows hijacking an active Keycloak session by triggering a new authentication process with the query parameter "prompt=login," prompting the user to re-enter their credentials. If the user cancels this re-authentication by selecting "Restart login," an account takeover may occur, as the new session, with a different SUB, will possess the same SID as the previous session.
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Analysis
by VulDB Data Team • 11/11/2025
The vulnerability identified as CVE-2023-6787 represents a critical session management flaw within the Keycloak identity and access management platform. This issue resides within the re-authentication mechanism of the org.keycloak.authentication package, specifically affecting how the system handles user session transitions during authentication processes. The flaw exploits a fundamental weakness in session handling that can be leveraged by malicious actors to manipulate active user sessions and potentially gain unauthorized access to user accounts.
The technical implementation of this vulnerability stems from an insufficient validation mechanism during the re-authentication process. When a user encounters a prompt with the query parameter "prompt=login," the system initiates a new authentication flow that should require credential re-entry. However, the vulnerability manifests when users select the "Restart login" option instead of properly authenticating. This action triggers an unexpected session state transition where the system creates a new session identifier with a different subject identifier SUB while maintaining the original session identifier SID. This design flaw creates a scenario where session hijacking becomes possible through session token manipulation.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on Keycloak for authentication services. The attack vector is particularly concerning because it requires minimal user interaction beyond the standard authentication flow, making it difficult to detect and prevent. The account takeover scenario occurs because the system fails to properly invalidate or validate the original session state when a user cancels the re-authentication process. This creates a window where an attacker could potentially leverage the compromised session state to impersonate legitimate users. The vulnerability aligns with CWE-613, which addresses inadequate session management and improper session invalidation, and it maps to ATT&CK technique T1566 related to credential access through social engineering or session manipulation.
The impact of this vulnerability extends beyond simple session hijacking to potentially enable broader account compromise and unauthorized access to protected resources. Organizations using Keycloak may experience unauthorized data access, privilege escalation, and potential lateral movement within their systems if attackers successfully exploit this flaw. The vulnerability's exploitation is particularly dangerous in environments where Keycloak serves as a central authentication point for multiple applications and services. Security teams should consider implementing immediate monitoring for unusual authentication patterns and session state transitions that could indicate exploitation attempts. The flaw demonstrates a critical gap in session lifecycle management and highlights the importance of robust session validation mechanisms in identity and access management systems.
Mitigation strategies for CVE-2023-6787 should include immediate patching of affected Keycloak versions and implementation of additional session validation controls. Organizations should review their authentication flow configurations to ensure proper handling of cancellation scenarios and implement stricter session invalidation procedures. Network monitoring should be enhanced to detect anomalous session behavior, particularly around SID and SUB identifier changes during authentication processes. The vulnerability serves as a reminder of the critical importance of proper session management in authentication systems and the need for comprehensive security testing of authentication flows. Organizations should also consider implementing additional security controls such as multi-factor authentication and session timeout mechanisms to reduce the risk of exploitation. Regular security assessments of authentication systems should be conducted to identify and remediate similar session management vulnerabilities that could compromise user accounts and system integrity.