CVE-2015-7546 in Identity
Summary
by MITRE
The identity service in OpenStack Identity (Keystone) before 2015.1.3 (Kilo) and 8.0.x before 8.0.2 (Liberty) and keystonemiddleware (formerly python-keystoneclient) before 1.5.4 (Kilo) and Liberty before 2.3.3 does not properly invalidate authorization tokens when using the PKI or PKIZ token providers, which allows remote authenticated users to bypass intended access restrictions and gain access to cloud resources by manipulating byte fields within a revoked token.
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Analysis
by VulDB Data Team • 07/15/2018
The vulnerability identified as CVE-2015-7546 represents a critical authorization bypass flaw within OpenStack Identity service components that affects multiple releases of Keystone and its supporting middleware libraries. This issue specifically targets the token invalidation mechanism when utilizing PKI or PKIZ token providers, creating a scenario where revoked tokens can still be exploited by authenticated attackers to maintain unauthorized access to cloud resources. The flaw stems from improper handling of token validation processes that fail to adequately check the revocation status of tokens, allowing attackers to manipulate specific byte fields within token structures to circumvent access controls.
The technical root cause of this vulnerability lies in the flawed token validation logic within the Keystone identity service where the system does not properly enforce token revocation checks for PKI and PKIZ token types. When tokens are revoked through standard administrative processes, the system should invalidate them immediately across all service components, but this validation fails to occur properly in the affected versions. Attackers can exploit this by manipulating the byte-level structure of revoked tokens, specifically targeting fields that control token validity and authorization status. This manipulation allows the system to accept previously revoked tokens as valid, effectively bypassing the intended authorization controls that should prevent access to cloud resources.
The operational impact of CVE-2015-7546 extends beyond simple unauthorized access to potentially compromising entire cloud environments where Keystone serves as the central identity management system. Organizations utilizing affected OpenStack releases face significant risk of privilege escalation attacks where authenticated users can maintain access to resources they should not have access to, potentially leading to data breaches, service disruption, and unauthorized resource consumption. The vulnerability affects both the Keystone service itself and the keystonemiddleware components that handle token validation for various OpenStack services, creating a widespread impact across the cloud infrastructure. This issue particularly threatens multi-tenant environments where proper isolation between users is critical for security.
Security mitigations for this vulnerability involve immediate patching of all affected OpenStack Identity service components to versions that properly handle token invalidation for PKI and PKIZ token providers. Organizations should implement comprehensive token revocation processes and regularly audit token usage patterns to detect potential exploitation attempts. The fix addresses the underlying CWE-284 access control vulnerability by ensuring proper token validation mechanisms are enforced, preventing attackers from manipulating byte fields within revoked tokens to maintain unauthorized access. Additionally, system administrators should consider implementing additional monitoring controls to detect unusual token usage patterns and establish more robust token lifecycle management processes. The ATT&CK framework categorizes this as a privilege escalation technique through credential manipulation, where attackers exploit weaknesses in authentication systems to maintain persistent access to cloud resources beyond their intended authorization scope.