CVE-2024-47616 in Pomerium
Summary
by MITRE • 10/03/2024
Pomerium is an identity and context-aware access proxy. The Pomerium databroker service is responsible for managing all persistent Pomerium application state. Requests to the databroker service API are authorized by the presence of a JSON Web Token (JWT) signed by a key known by all Pomerium services in the same deployment. However, incomplete validation of this JWT meant that some service account access tokens would incorrectly be treated as valid for the purpose of databroker API authorization. Improper access to the databroker API could allow exfiltration of user info, spoofing of user sessions, or tampering with Pomerium routes, policies, and other settings. A Pomerium deployment is susceptible to this issue if all of the following conditions are met, you have issued a service account access token using Pomerium Zero or Pomerium Enterprise, the access token has an explicit expiration date in the future, and the core Pomerium databroker gRPC API is not otherwise secured by network access controls. This vulnerability is fixed in 0.27.1.
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Analysis
by VulDB Data Team • 11/08/2024
The vulnerability identified as CVE-2024-47616 affects Pomerium's databroker service, which serves as the central component for managing persistent application state within Pomerium deployments. This service operates as a critical infrastructure element responsible for maintaining user sessions, route configurations, policy definitions, and other essential operational data. The databroker service API requires authentication through JSON Web Tokens (JWT) that are signed by a shared key accessible to all Pomerium services within the same deployment. This design approach relies on the principle that only legitimate service components should be able to access the databroker API, as they possess the necessary cryptographic key for token validation. The security model assumes that any valid JWT signed with this shared key represents legitimate service access, but this assumption contained a critical flaw in the validation process. The incomplete JWT validation mechanism failed to properly verify certain service account access tokens, allowing some tokens to be incorrectly accepted as valid for databroker API authorization purposes.
The technical flaw stems from insufficient validation logic within the JWT processing pipeline of the databroker service. When service account access tokens are generated through Pomerium Zero or Pomerium Enterprise, these tokens contain specific attributes including expiration dates and service identifiers. However, the validation routine did not adequately check all required token attributes before granting access to the databroker API. This incomplete validation creates an authorization bypass vulnerability where malicious actors or compromised services could potentially impersonate legitimate service accounts. The flaw specifically impacts tokens that have explicit future expiration dates, suggesting that the validation process may have been optimized for certain token types while neglecting others. According to CWE classification, this vulnerability aligns with CWE-287 which addresses improper authentication issues, and potentially CWE-345 which covers insufficient verification of data authenticity. The vulnerability also demonstrates characteristics of privilege escalation through token manipulation, as identified in ATT&CK framework under technique T1078 for valid accounts and T1566 for credential harvesting.
The operational impact of this vulnerability extends beyond simple unauthorized access to include significant data exposure and system integrity compromise. An attacker who exploits this vulnerability could extract sensitive user information stored within the databroker, potentially including session data, user identifiers, and authentication details. The ability to spoof user sessions represents a particularly dangerous aspect, as it could enable persistent unauthorized access to protected resources without detection. Additionally, the vulnerability allows for manipulation of core Pomerium configurations including route definitions, policy settings, and other critical operational parameters. This tampering capability could result in service disruption, unauthorized access to sensitive systems, or redirection of traffic to malicious endpoints. The attack surface is further expanded by the fact that this vulnerability only requires a specific combination of deployment conditions, making it potentially exploitable in production environments where network access controls are not properly implemented. Organizations using Pomerium Enterprise or Pomerium Zero with service account tokens that have future expiration dates face significant risk if they have not implemented additional network-level security controls.
The mitigation strategy for CVE-2024-47616 requires immediate deployment of Pomerium version 0.27.1 which contains the necessary validation fixes. Organizations should also implement additional network security controls to restrict access to the databroker gRPC API, ensuring that only authorized service components can reach this critical endpoint. The remediation process should include thorough review of all service account tokens within the deployment to identify potentially compromised access. Network segmentation and access control lists should be implemented to prevent unauthorized systems from communicating with the databroker service. Security teams should also conduct comprehensive audits of their Pomerium configurations to ensure that all deployment conditions are properly addressed. The vulnerability highlights the importance of proper token validation and the potential consequences of incomplete security checks in distributed systems. Organizations should consider implementing additional monitoring for unauthorized access attempts to the databroker API, as well as regular security assessments of their identity and access management infrastructure. This vulnerability serves as a reminder of the critical importance of robust authentication validation mechanisms and the potential for seemingly minor implementation flaws to create significant security risks in complex distributed systems.