CVE-2017-8034 in Cloud Foundry
Summary
by MITRE
The Cloud Controller and Router in Cloud Foundry (CAPI-release capi versions prior to v1.32.0, Routing-release versions prior to v0.159.0, CF-release versions prior to v267) do not validate the issuer on JSON Web Tokens (JWTs) from UAA. With certain multi-zone UAA configurations, zone administrators are able to escalate their privileges.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/27/2019
The vulnerability identified as CVE-2017-8034 resides within the Cloud Foundry platform's Cloud Controller and Router components, specifically affecting the CAPI-release capi versions prior to v1.32.0 and routing-release versions prior to v0.159.0. This flaw manifests in the improper validation of JSON Web Token (JWT) issuers originating from the User Account and Authentication (UAA) service, creating a critical security gap that undermines the platform's authentication framework. The issue is particularly concerning within multi-zone UAA configurations where administrative privileges can be escalated by zone administrators who should not possess such elevated access rights.
The technical flaw stems from the absence of proper issuer validation within the Cloud Foundry components, allowing malicious actors to manipulate JWT tokens by forging or substituting issuer information. This vulnerability directly relates to CWE-295 which addresses "Improper Certificate Validation" and CWE-347 which covers "Improper Verification of Cryptographic Signature." The flaw enables an attacker to bypass the normal authentication mechanisms that should prevent zone administrators from accessing resources outside their designated zones, effectively breaking down the isolation boundaries that should exist between different administrative domains within the platform.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the security model of multi-zone Cloud Foundry deployments. Zone administrators who should only have access to their specific zone can potentially access resources, data, and administrative functions across other zones, creating a severe lateral movement capability for attackers. This issue affects CF-release versions prior to v267, indicating it impacts a substantial portion of the platform's user base and creates widespread potential for exploitation across organizations utilizing Cloud Foundry in multi-zone configurations.
The security implications of CVE-2017-8034 align with several ATT&CK techniques including privilege escalation through token manipulation and lateral movement by exploiting trust relationships between system components. The vulnerability enables attackers to leverage the trust relationship between the UAA service and the Cloud Controller/Router components, essentially allowing them to impersonate legitimate users and gain unauthorized access to sensitive resources. Organizations implementing Cloud Foundry in production environments must consider this vulnerability as a critical threat to their multi-zone deployment security posture, particularly those utilizing UAA configurations that rely on zone-based administrative separation.
Mitigation strategies for this vulnerability require immediate patching of affected components to versions that properly validate JWT issuers against expected UAA configurations. Organizations should implement strict issuer validation policies that verify the authenticity of the signing authority for all JWT tokens and ensure that the UAA service is properly configured to enforce zone boundaries. Network segmentation and monitoring should be enhanced to detect unusual access patterns that might indicate exploitation attempts. Additionally, security teams should conduct comprehensive audits of their Cloud Foundry deployments to verify that zone isolation is properly maintained and that no unauthorized cross-zone access has occurred. The fix addresses the core issue by implementing proper JWT validation mechanisms that prevent forged or manipulated tokens from being accepted by the Cloud Controller and Router components, thereby restoring the intended security boundaries within multi-zone Cloud Foundry deployments.