CVE-2013-4294 in Keystone
Summary
by MITRE
The (1) mamcache and (2) KVS token backends in OpenStack Identity (Keystone) Folsom 2012.2.x and Grizzly before 2013.1.4 do not properly compare the PKI token revocation list with PKI tokens, which allow remote attackers to bypass intended access restrictions via a revoked PKI token.
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Analysis
by VulDB Data Team • 01/07/2022
The vulnerability described in CVE-2013-4294 represents a critical flaw in the OpenStack Identity service known as Keystone, specifically affecting the memcache and KVS token backends during the Folsom and Grizzly release cycles. This issue stems from improper comparison mechanisms between revoked PKI tokens and the revocation list, creating a significant security gap that allows malicious actors to exploit the system's authentication controls. The vulnerability exists within the token validation process where the system fails to correctly verify whether a presented token has been properly revoked, effectively undermining the entire token-based access control mechanism.
The technical root cause of this vulnerability lies in the flawed implementation of token revocation checking within Keystone's backend storage systems. When PKI tokens are revoked, the system maintains a revocation list that should prevent any further use of those tokens. However, the memcache and KVS backends fail to properly validate against this list during token verification, creating a scenario where a revoked token can still be accepted as valid by the authentication system. This misimplementation allows attackers to reuse tokens that should have been invalidated, bypassing the intended access restrictions and potentially gaining unauthorized access to cloud resources.
From an operational impact perspective, this vulnerability presents a severe risk to OpenStack deployments as it fundamentally compromises the authentication and authorization mechanisms that protect cloud infrastructure. Remote attackers who can obtain a revoked token can essentially bypass access controls and gain unauthorized access to cloud services, potentially leading to data breaches, resource consumption, and privilege escalation attacks. The vulnerability affects multiple versions of OpenStack Keystone, making it widespread across various deployments that had not yet implemented the necessary patches. This flaw particularly impacts multi-tenant cloud environments where proper access control is critical for maintaining security boundaries between different users and projects.
The vulnerability aligns with CWE-284, which addresses improper access control, and demonstrates how inadequate token management can lead to privilege escalation and unauthorized access. From an ATT&CK framework perspective, this issue maps to privilege escalation techniques where adversaries exploit weaknesses in authentication systems to maintain persistent access. Organizations using affected OpenStack versions should immediately implement the patches released by the OpenStack community, which address the token comparison logic in both memcache and KVS backends. Additionally, security teams should conduct thorough audits of their token management systems and consider implementing additional monitoring for suspicious authentication patterns that might indicate exploitation attempts. The fix involves correcting the token revocation list comparison logic to ensure that all revoked tokens are properly rejected during authentication requests, thereby restoring the intended security controls within the Keystone service.