CVE-2017-8031 in Cloud Foundry
Summary
by MITRE
An issue was discovered in Cloud Foundry Foundation cf-release (all versions prior to v279) and UAA (30.x versions prior to 30.6, 45.x versions prior to 45.4, 52.x versions prior to 52.1). In some cases, the UAA allows an authenticated user for a particular client to revoke client tokens for other users on the same client. This occurs only if the client is using opaque tokens or JWT tokens validated using the check_token endpoint. A malicious actor could cause denial of service.
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Analysis
by VulDB Data Team • 12/10/2019
The vulnerability described in CVE-2017-8031 represents a critical authorization flaw within the Cloud Foundry UAA (User Account and Authentication) service that affects multiple versions of the cf-release platform. This issue stems from improper access control mechanisms within the token revocation process, specifically impacting how the system handles token management for authenticated clients. The vulnerability exists in versions prior to v279 of cf-release and specific patch versions of UAA including 30.6, 45.4, and 52.1, creating a persistent security gap that could be exploited across various Cloud Foundry deployments. The flaw manifests when an authenticated user associated with a particular client application can perform token revocation actions against tokens belonging to other users within the same client context, fundamentally undermining the principle of least privilege and user isolation.
The technical implementation of this vulnerability resides in the UAA's token management subsystem where the system fails to properly validate whether the requesting user has legitimate authorization to revoke tokens belonging to other users. When clients utilize opaque tokens or JWT tokens validated through the check_token endpoint, the system's access control checks become insufficient, allowing unauthorized token revocation operations. This issue is categorized under CWE-284 Access Control Bypass, specifically manifesting as improper access control during token management operations. The flaw operates at the application level within the UAA service, where the token revocation endpoint does not properly enforce user-specific authorization boundaries, enabling cross-user token manipulation.
The operational impact of CVE-2017-8031 extends beyond simple privilege escalation to create significant denial of service conditions within Cloud Foundry environments. A malicious authenticated user can systematically revoke tokens belonging to other legitimate users within the same client application, effectively locking them out of system resources and services. This creates cascading effects throughout the platform as users lose access to their applications and services, potentially disrupting business operations and service availability. The vulnerability can be exploited systematically to cause widespread service degradation, making it particularly dangerous in multi-tenant environments where multiple users share the same client applications. From an ATT&CK framework perspective, this vulnerability maps to T1078 Valid Accounts and T1499 Endpoint Denial of Service, enabling both unauthorized access and service disruption capabilities.
Mitigation strategies for CVE-2017-8031 require immediate deployment of patched versions of cf-release and UAA components, specifically upgrading to versions v279 or later for cf-release and the respective patch versions mentioned. Organizations should implement additional monitoring and logging of token revocation activities to detect anomalous behavior patterns that might indicate exploitation attempts. The security configuration should be reviewed to ensure proper token validation and access control mechanisms are in place, particularly for clients utilizing opaque tokens or JWT validation through check_token endpoints. Network segmentation and access controls should be enhanced to limit the scope of potential exploitation, while regular security audits should verify that proper authorization boundaries are maintained. Additionally, implementing automated alerting for token revocation events can help detect and respond to unauthorized token manipulation attempts in real-time, providing visibility into potential exploitation activities and supporting incident response procedures.