CVE-2024-4195 in Mattermost
Summary
by MITRE • 04/26/2024
Mattermost versions 9.6.0, 9.5.x before 9.5.3, and 8.1.x before 8.1.12 fail to fully validate role changes, which allows an attacker authenticated as a team admin to promote guests to team admins via crafted HTTP requests.
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Analysis
by VulDB Data Team • 05/12/2025
The vulnerability described in CVE-2024-4195 represents a critical authorization flaw within Mattermost's access control mechanisms that directly impacts the platform's security posture. This issue affects specific versions of Mattermost including 9.6.0, all 9.5.x versions prior to 9.5.3, and 8.1.x versions before 8.1.12, indicating a widespread impact across multiple release lines. The core problem stems from insufficient validation of role modifications within the system's permission framework, creating a pathway for privilege escalation attacks that can fundamentally compromise team security boundaries.
The technical flaw manifests through improper validation of role change requests within the Mattermost platform's HTTP request handling system. When authenticated team administrators attempt to modify user roles, the system fails to adequately verify that such modifications comply with established security policies and role hierarchies. This validation gap allows attackers to craft specially formatted HTTP requests that bypass normal access control checks, enabling them to elevate guest users to team administrator privileges. The vulnerability specifically targets the role assignment functionality within team contexts, exploiting a weakness in the input validation process that should enforce proper authorization boundaries between different user roles.
The operational impact of this vulnerability is severe and multifaceted, as it allows attackers with minimal privileges to gain elevated access within their targeted team environments. Once a guest user is promoted to team administrator status, the attacker gains comprehensive control over team-specific configurations, user management, channel permissions, and access to sensitive communications within that team. This privilege escalation capability can lead to unauthorized data access, configuration changes, and potential lateral movement within the Mattermost environment. The vulnerability essentially undermines the fundamental security model of team-based access control, where guest users should remain restricted to read-only or limited access permissions.
From a cybersecurity framework perspective, this vulnerability maps directly to CWE-285 (Improper Authorization) and represents a clear violation of the principle of least privilege. The flaw aligns with ATT&CK technique T1078.004 (Valid Accounts: Cloud Accounts) as it exploits legitimate authentication mechanisms to achieve unauthorized privilege escalation. Organizations relying on Mattermost for secure communications and collaboration face significant risk exposure, particularly in environments where guest access is permitted and where sensitive data is managed within team structures. The vulnerability's impact extends beyond immediate access control breaches to potentially enable more sophisticated attacks including data exfiltration, configuration manipulation, and persistent access establishment within the platform.
The recommended mitigation strategy involves immediate deployment of the patched versions mentioned in the CVE description, specifically upgrading to Mattermost 9.5.3 or later for 9.5.x releases and 8.1.12 or later for 8.1.x releases. Organizations should also implement additional monitoring of role change activities and establish automated alerting for unusual privilege escalation events. Network segmentation and access controls should be reviewed to limit the potential impact of successful exploitation, while security teams should conduct thorough audits of existing user roles and permissions to identify any potential compromise. Regular security assessments of authentication and authorization mechanisms should be implemented to prevent similar vulnerabilities from emerging in the future.