CVE-2021-37864 in Mattermost
Summary
by MITRE • 01/18/2022
Mattermost 6.1 and earlier fails to sufficiently validate permissions while viewing archived channels, which allows authenticated users to view contents of archived channels even when this is denied by system administrators by directly accessing the APIs.
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Analysis
by VulDB Data Team • 01/26/2022
The vulnerability described in CVE-2021-37864 represents a critical access control flaw within the Mattermost collaboration platform version 6.1 and earlier. This issue stems from insufficient permission validation mechanisms that govern user access to archived channels within the system. The flaw specifically affects the API endpoints responsible for channel content retrieval, where authenticated users can bypass intended access restrictions through direct API calls. The vulnerability exists in the platform's authorization logic, which fails to properly enforce channel access policies when users attempt to view archived content.
From a technical perspective, this vulnerability manifests as a failure in the permission validation process that occurs when users attempt to access archived channels through the application programming interface. The system's access control mechanism does not adequately verify whether the requesting user possesses the necessary privileges to view archived channel contents, even when administrators have explicitly restricted such access. This represents a classic authorization bypass vulnerability that falls under the CWE-285 category of improper authorization controls. The flaw enables malicious or unauthorized users to circumvent the intended security boundaries that protect archived content from unauthorized viewing.
The operational impact of this vulnerability is significant for organizations relying on Mattermost for secure communications and collaboration. When users can access archived channel contents without proper authorization, it creates potential data exposure risks that could compromise sensitive information shared within teams and departments. This vulnerability undermines the security posture of the platform by allowing users to access historical communications that should remain restricted based on administrative policies. The direct API access method means that attackers can exploit this vulnerability programmatically without requiring complex social engineering or additional attack vectors, making the exploitation relatively straightforward and automated.
Organizations utilizing Mattermost versions prior to 6.2 should immediately implement mitigations to address this vulnerability. The primary recommended action involves upgrading to Mattermost version 6.2 or later, where the permission validation mechanisms have been strengthened to properly enforce channel access controls for archived content. Additionally, system administrators should conduct thorough audits of existing channel access policies and ensure that appropriate restrictions are in place for archived channels. The vulnerability aligns with ATT&CK technique T1078.004 which covers valid accounts and privilege escalation through improper access control mechanisms. Organizations should also consider implementing network-level controls and monitoring for unusual API access patterns that might indicate exploitation attempts. The security implications extend beyond simple content exposure to potential compliance violations in regulated environments where proper access controls are mandatory for data protection requirements.