CVE-2023-1774 in Mattermost
Summary
by MITRE • 03/31/2023
When processing an email invite to a private channel on a team, Mattermost fails to validate the inviter's permission to that channel, allowing an attacker to invite themselves to a private channel.
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Analysis
by VulDB Data Team • 04/21/2023
The vulnerability identified as CVE-2023-1774 represents a critical access control flaw within the Mattermost collaboration platform that undermines the security of private channels and team-based communications. This issue specifically affects the validation mechanisms that govern who can invite users to private channels within team environments, creating a pathway for unauthorized access that directly violates fundamental security principles of least privilege and proper authorization controls. The flaw exists in the platform's permission validation logic, where the system fails to properly verify whether the user initiating an invitation possesses the necessary credentials or permissions to extend access to a specific private channel.
The technical implementation of this vulnerability stems from inadequate input validation and permission checking routines within Mattermost's channel management subsystem. When a user attempts to invite another user to a private channel, the system should verify that the inviter has explicit authorization to add members to that particular channel. However, the current implementation bypasses this crucial validation step, allowing any authenticated user to potentially invite themselves or others to channels where they should not have access. This failure aligns with CWE-284, which categorizes improper access control vulnerabilities, specifically addressing insufficient authorization checks that permit unauthorized users to perform privileged operations.
The operational impact of CVE-2023-1774 extends beyond simple unauthorized access, creating potential for data exfiltration, information disclosure, and disruption of collaborative workflows within organizations that rely on Mattermost for secure communications. Attackers could exploit this vulnerability to gain access to sensitive project information, confidential discussions, or proprietary data stored within private channels that should only be accessible to authorized team members. This vulnerability particularly affects organizations implementing zero-trust security models where private channels serve as secure repositories for sensitive information, as it undermines the integrity of these security boundaries. The risk is amplified in environments where Mattermost serves as a primary communication platform for critical business operations, development teams, or compliance-sensitive projects.
Organizations utilizing Mattermost should immediately implement mitigations including updating to patched versions of the platform, reviewing and strengthening channel permission policies, and conducting comprehensive audits of existing private channel access controls. System administrators should also implement additional monitoring and alerting mechanisms to detect unauthorized invitation attempts and investigate any suspicious activity within private channel environments. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and persistence within communication platforms, potentially enabling attackers to establish footholds in secure team environments and maintain access to sensitive information. The remediation process should include comprehensive security testing of permission validation logic and implementation of automated checks to ensure that all invitation requests properly validate user credentials against channel access controls.