CVE-2020-7955 in Consul
Summary
by MITRE
HashiCorp Consul and Consul Enterprise 1.4.1 through 1.6.2 did not uniformly enforce ACLs across all API endpoints, resulting in potential unintended information disclosure. Fixed in 1.6.3.
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Analysis
by VulDB Data Team • 03/27/2024
HashiCorp Consul and Consul Enterprise versions 1.4.1 through 1.6.2 contained a critical access control vulnerability that undermined the integrity of the application's authentication and authorization mechanisms. This flaw manifested as inconsistent enforcement of Access Control Lists (ACLs) across the system's various API endpoints, creating potential pathways for unauthorized access to sensitive data and system information. The vulnerability specifically affected the uniform application of ACL policies, where some endpoints failed to properly validate user permissions before executing operations or returning information. This inconsistency created a scenario where authenticated users could potentially access resources or data that should have been restricted based on their assigned ACL policies.
The technical nature of this vulnerability stems from improper implementation of access control validation logic within the Consul API framework. When users made requests to various endpoints, the system did not consistently verify whether the requesting entity possessed sufficient privileges to perform the requested operation or access the requested information. This flaw falls under the CWE-284 access control weakness category, specifically addressing insufficient access control mechanisms. The vulnerability allowed for information disclosure scenarios where users with limited permissions could potentially extract data or system information that should have been protected by stricter ACL enforcement. Attackers could exploit this inconsistency to gain unauthorized visibility into service configurations, health check results, and other sensitive operational details that are typically restricted to authorized personnel only.
The operational impact of this vulnerability extended beyond simple data exposure, potentially enabling more sophisticated attack vectors within the Consul environment. Organizations using affected versions could experience unauthorized access to service discovery information, which might reveal internal network topology and service dependencies to malicious actors. This information disclosure could facilitate further attacks such as service enumeration, reconnaissance for privilege escalation, or targeting of specific services within the Consul mesh. The vulnerability particularly affected enterprise environments where Consul serves as a critical component of service mesh architecture, potentially compromising the security posture of distributed applications that rely on Consul for service discovery and configuration management. The issue created a persistent risk where even authenticated users could bypass expected access controls through exploitation of the inconsistent ACL enforcement.
Mitigation strategies for this vulnerability required immediate upgrade to Consul version 1.6.3 or later, which implemented uniform ACL enforcement across all API endpoints. Organizations should also conduct comprehensive audits of their existing ACL policies to identify any potential misconfigurations that could have been exploited prior to the fix. Security teams should review and validate access control configurations, ensuring that all API endpoints properly enforce the intended authorization policies. The remediation process should include thorough testing of ACL configurations to verify that access controls are consistently applied across all endpoints. Additionally, organizations should implement monitoring solutions to detect anomalous access patterns that might indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to privilege escalation and credential access, where attackers could leverage inconsistent access controls to expand their operational capabilities within the Consul environment. Regular security assessments and continuous monitoring of access control mechanisms should be implemented to prevent similar issues from emerging in the future.