CVE-2016-8218 in Cloud Foundry
Summary
by MITRE
An issue was discovered in Cloud Foundry Foundation routing-release versions prior to 0.142.0 and cf-release versions 203 to 231. Incomplete validation logic in JSON Web Token (JWT) libraries can allow unprivileged attackers to impersonate other users to the routing API, aka an "Unauthenticated JWT signing algorithm in routing" issue.
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Analysis
by VulDB Data Team • 10/16/2019
The vulnerability identified as CVE-2016-8218 represents a critical security flaw in the Cloud Foundry Foundation's routing-release component affecting versions prior to 0.142.0 and cf-release versions 203 through 231. This issue stems from incomplete validation logic within JSON Web Token (JWT) libraries that governs authentication and authorization mechanisms within the Cloud Foundry platform. The flaw specifically targets the routing API component which serves as a critical gateway for traffic management and service discovery within Cloud Foundry deployments. The vulnerability enables unprivileged attackers to exploit weak JWT validation processes and impersonate legitimate users within the routing system, fundamentally undermining the platform's access control mechanisms.
The technical implementation of this vulnerability resides in the JWT library's handling of signing algorithms where the validation logic fails to properly verify the cryptographic signature verification process. This incomplete validation allows attackers to manipulate JWT tokens by changing the signing algorithm from a secure algorithm like RS256 to a weaker algorithm such as HS256, which uses a shared secret that can be easily guessed or extracted. The flaw manifests when the routing component accepts tokens without properly validating that the signing algorithm matches the expected cryptographic requirements, creating a pathway for attackers to forge tokens and gain unauthorized access to routing services. This issue directly relates to CWE-347, which addresses the lack of proper validation of cryptographic signatures, and aligns with ATT&CK technique T1550.001 for using valid credentials obtained through credential manipulation.
The operational impact of this vulnerability extends beyond simple privilege escalation as it compromises the integrity of the entire routing infrastructure within Cloud Foundry deployments. Attackers who successfully exploit this vulnerability can redirect traffic to malicious endpoints, gain access to sensitive routing information, and potentially disrupt services across the platform. The implications are particularly severe in multi-tenant environments where routing decisions directly affect service availability and data flow between applications. Organizations using affected versions of Cloud Foundry face risks of data interception, service disruption, and potential lateral movement within their cloud infrastructure. The vulnerability essentially undermines the trust model of the platform's routing system, allowing unauthorized actors to manipulate traffic flow and access routing APIs without proper authentication.
Mitigation strategies for CVE-2016-8218 require immediate patching of affected components to version 0.142.0 or later of routing-release and cf-release 232 or higher. Organizations should implement comprehensive monitoring of routing API access logs to detect anomalous token usage patterns and unauthorized access attempts. Security teams must validate that JWT libraries are properly configured to enforce strict algorithm validation and reject tokens that specify weak or insecure signing algorithms. Network segmentation and access controls should be reinforced around routing APIs to limit exposure even if token forgery occurs. Additionally, organizations should conduct thorough security assessments of their Cloud Foundry deployments to identify any other components that might be vulnerable to similar JWT validation issues, ensuring that all cryptographic validation processes are properly implemented and tested according to industry best practices. The fix addresses the core validation logic issue by enforcing proper algorithm verification and ensuring that routing components reject tokens with insecure signature methods that could be exploited for impersonation attacks.