CVE-2021-36775 in Rancher
Summary
by MITRE • 04/04/2022
a Improper Access Control vulnerability in SUSE Rancher allows users to keep privileges that should have been revoked. This issue affects: SUSE Rancher Rancher versions prior to 2.4.18; Rancher versions prior to 2.5.12; Rancher versions prior to 2.6.3.
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Analysis
by VulDB Data Team • 04/06/2022
The CVE-2021-36775 vulnerability represents a critical improper access control flaw within SUSE Rancher container management platform that undermines the system's privilege management mechanisms. This vulnerability specifically targets the authorization controls that govern user permissions and access rights within the Rancher environment, allowing authenticated users to maintain elevated privileges that should have been revoked upon logout or role changes. The flaw exists in the platform's session management and access control enforcement logic, creating a persistent security weakness that can be exploited by both internal and external attackers. The vulnerability affects multiple versions of the Rancher platform including versions prior to 2.4.18, 2.5.12, and 2.6.3, indicating a widespread impact across the product's release lifecycle. This type of vulnerability falls under CWE-284 which specifically addresses improper access control issues in software systems, where the system fails to properly enforce authorization mechanisms that should prevent unauthorized access to resources or functionality.
The technical implementation of this access control flaw stems from inadequate session validation and privilege revocation processes within the Rancher platform. When users perform actions that should result in privilege demotion or complete access revocation, the system fails to properly invalidate their session tokens or update their access permissions. This creates a scenario where compromised or malicious users can continue to operate with elevated privileges even after their legitimate access rights should have been terminated. The vulnerability essentially allows privilege escalation through session hijacking or persistence mechanisms that bypass normal authorization checks. Attackers could exploit this by maintaining access to sensitive cluster operations, resource management functions, or administrative capabilities that should only be available to authorized personnel with specific roles and permissions. The flaw particularly impacts multi-tenant environments where different users have varying levels of access control, as it allows unauthorized persistence of elevated privileges across user sessions.
The operational impact of CVE-2021-36775 extends beyond simple privilege escalation to encompass potential data compromise, system integrity violations, and unauthorized resource manipulation within Rancher-managed Kubernetes clusters. Organizations using affected Rancher versions face significant risk of unauthorized access to containerized applications, cluster configurations, and sensitive operational data. The vulnerability enables attackers to perform operations such as deploying malicious workloads, modifying cluster settings, accessing confidential information, or disrupting normal cluster operations. This risk is compounded by the fact that the flaw affects multiple version branches, meaning that organizations across different Rancher release cycles remain vulnerable. The persistence of these elevated privileges creates a long-term security exposure that can remain undetected for extended periods, potentially allowing attackers to establish backdoors, exfiltrate data, or cause service disruptions. From an operational standpoint, this vulnerability undermines the fundamental security model of container orchestration platforms where access control is paramount for maintaining cluster security and isolation.
Organizations should immediately implement mitigations including upgrading to patched versions of Rancher that address the access control flaws in CVE-2021-36775. The recommended remediation involves upgrading to Rancher versions 2.4.18, 2.5.12, or 2.6.3, which contain the necessary fixes for proper privilege revocation and session management. System administrators should conduct immediate vulnerability assessments to identify any compromised sessions or unauthorized access patterns within their Rancher environments. Additional mitigations include implementing enhanced monitoring for unusual privilege usage patterns, enforcing strict session timeout policies, and conducting regular access reviews to ensure proper privilege allocation. Organizations should also consider implementing network segmentation and additional authentication controls to limit the impact of potential exploitation. The vulnerability's classification under ATT&CK technique T1078 for valid accounts and T1484 for domain controller privilege escalation highlights the need for comprehensive security monitoring and incident response procedures to detect and respond to unauthorized privilege usage. Security teams must also review and audit existing access control policies to ensure proper role-based access controls are enforced throughout the Rancher platform and its integrated Kubernetes clusters.