CVE-2026-2299 in Google Drive Plugin
Summary
by MITRE • 06/25/2026
The Mattermost Google Drive plugin before version 1.1.0 fails to validate channel membership in the file creation endpoint, allowing authenticated users with a connected Google account to share Google Drive files to unauthorized private channels and disclose private channel membership.
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Analysis
by VulDB Data Team • 06/26/2026
The vulnerability in the Mattermost Google Drive plugin affects versions prior to 1.1.0 and represents a critical access control flaw that undermines the security model of private communications within the platform. This issue stems from insufficient validation of channel membership during file creation operations, creating a pathway for authenticated users to bypass normal permission controls. The flaw specifically impacts the file creation endpoint where users with valid Google account connections can manipulate the sharing behavior of their files, enabling them to distribute content to channels they should not have access to based on standard Mattermost access controls.
The technical nature of this vulnerability aligns with CWE-284 Access Control Issues, where improper access control mechanisms allow unauthorized entities to perform actions they should not be permitted to execute. The plugin fails to verify whether the authenticated user has legitimate membership in the target private channel before allowing file sharing operations, effectively creating a privilege escalation vector. This validation gap exists specifically within the integration between Mattermost's channel management system and Google Drive's sharing capabilities, where the plugin does not properly cross-reference user permissions against channel membership lists during the file creation process.
From an operational perspective, this vulnerability exposes organizations to significant security risks including unauthorized data disclosure and potential information leakage across private channels. Attackers could exploit this flaw to gain access to sensitive conversations and shared files within private channels they do not belong to, potentially compromising confidential business communications, intellectual property, or personal information. The impact extends beyond simple file sharing as it also reveals the membership structure of private channels, providing attackers with insights into the organizational communication patterns and potentially exposing the existence of sensitive working groups or project teams.
The attack surface for this vulnerability is particularly concerning given that it requires only authentication to Mattermost with a connected Google account, making it accessible to any user who has already established their credentials within the system. This means that even users who have not been explicitly granted access to certain private channels can leverage their Google Drive integration to bypass normal channel membership restrictions. The vulnerability operates at the intersection of two major security domains - collaboration platform access controls and cloud storage sharing mechanisms - creating a complex threat scenario where traditional perimeter-based security measures may not prevent exploitation.
Organizations should immediately implement mitigations including updating to version 1.1.0 or later of the Mattermost Google Drive plugin, which addresses the channel membership validation issue through proper access control checks. Additionally, administrators should conduct comprehensive audits of channel memberships and file sharing activities within their Mattermost environments, particularly focusing on private channels that contain sensitive information. Network monitoring solutions should be configured to detect unusual file sharing patterns or attempts to access unauthorized channels. The implementation of principle of least privilege controls for Google Drive integrations and regular security assessments of third-party plugin configurations will help prevent similar vulnerabilities from arising in other integrated systems.
This vulnerability demonstrates the importance of proper input validation and access control enforcement in integrated collaboration platforms, particularly when connecting with external services like Google Drive that have their own sharing mechanisms. The flaw represents a classic case of insufficient authorization checking where the system assumes that because a user has authenticated access to one service, they should automatically have access to related functionality within connected systems. Security teams should consider implementing additional logging and alerting for file sharing operations, especially those involving cross-platform integrations, to detect potential exploitation attempts and maintain comprehensive audit trails for security investigations.
The broader implications of this vulnerability extend to organizations that rely heavily on integrated collaboration platforms where third-party plugins create additional attack surfaces. It highlights the need for robust security testing practices during plugin integration and continuous monitoring of user access patterns within collaborative environments. Organizations should establish clear policies regarding plugin security reviews, regular updates, and the implementation of compensating controls when integrating with external services that may introduce access control weaknesses. The vulnerability also underscores the importance of maintaining up-to-date security patches across all integrated components of enterprise collaboration platforms to prevent exploitation of known flaws in third-party integrations.
The attack pattern for this vulnerability aligns with ATT&CK technique T1078 Valid Accounts, where attackers leverage legitimate credentials to perform unauthorized actions within systems. The exploitation process involves using authenticated access to create file shares that bypass normal channel membership validation checks, effectively allowing lateral movement through the collaboration platform's permission model. Security teams should monitor for anomalous sharing behaviors and implement automated controls that enforce proper channel membership verification during file creation operations to prevent this type of unauthorized access from occurring in production environments.