CVE-2017-4991 in Cloud Foundry
Summary
by MITRE
An issue was discovered in Cloud Foundry Foundation cf-release versions prior to v260; UAA release 2.x versions prior to v2.7.4.16, 3.6.x versions prior to v3.6.10, 3.9.x versions prior to v3.9.12, and other versions prior to v3.17.0; and UAA bosh release (uaa-release) 13.x versions prior to v13.14, 24.x versions prior to v24.9, 30.x versions prior to 30.2, and other versions prior to v36. Privileged users in one zone are allowed to perform a password reset for users in a different zone.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/16/2019
The vulnerability described in CVE-2017-4991 represents a critical authorization flaw within the Cloud Foundry platform's User Account and Authentication (UAA) system. This issue affects multiple versions of the cf-release and UAA bosh release components, specifically targeting the zone isolation mechanisms that are fundamental to Cloud Foundry's multi-tenant architecture. The vulnerability stems from improper access controls that allow malicious actors with privileged credentials in one operational zone to exploit the password reset functionality for accounts in different zones, effectively bypassing the security boundaries that should separate tenant environments.
The technical implementation of this vulnerability resides in the UAA service's authentication and authorization logic where the zone validation checks are insufficient or improperly enforced during password reset operations. When a privileged user in one zone attempts to reset a password for another user, the system fails to properly verify that the target user belongs to the same zone as the requesting user. This flaw operates at the application layer and specifically impacts the UAA's user management APIs, where the zone attribute is not consistently validated during sensitive operations such as password reset requests. The vulnerability is classified under CWE-284 which describes improper access control, and aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation through unauthorized access to user accounts.
The operational impact of this vulnerability is severe for Cloud Foundry deployments that rely on zone-based isolation for multi-tenant security. An attacker who gains access to any privileged account in one zone can potentially compromise user accounts across multiple zones, leading to unauthorized access to sensitive data, privilege escalation, and potential lateral movement within the platform. This vulnerability undermines the fundamental security model of Cloud Foundry's multi-zone architecture, where zones are designed to provide isolation between different tenants or environments. The attack surface extends beyond simple credential theft to include potential data exfiltration, service disruption, and unauthorized modification of user accounts across the entire platform.
Mitigation strategies for CVE-2017-4991 require immediate patching of affected UAA components to versions that properly enforce zone boundaries during password reset operations. Organizations should implement strict version control policies to ensure all cf-release and UAA bosh release components are updated to secure versions, with particular attention to the specific version ranges mentioned in the vulnerability advisory. Network segmentation and additional access controls should be implemented to limit the blast radius of compromised privileged accounts, while monitoring should be enhanced to detect unauthorized password reset activities across zone boundaries. Security teams should also conduct comprehensive audits of their Cloud Foundry deployments to identify and remediate any custom implementations that may have introduced additional vulnerabilities. The remediation process should include thorough testing of updated components to ensure that zone isolation functionality works correctly and that legitimate administrative operations continue to function as expected.