CVE-2026-2463 in Mattermost
Summary
by MITRE • 03/16/2026
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to filter invite IDs based on user permissions, which allows regular users to bypass access control restrictions and register unauthorized accounts via leaked invite IDs during team creation.. Mattermost Advisory ID: MMSA-2025-00565
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Analysis
by VulDB Data Team • 03/20/2026
The vulnerability described in CVE-2026-2463 represents a critical access control flaw within Mattermost's team invitation system that directly undermines the platform's security model. This issue affects multiple versions of Mattermost including 11.3.0 and earlier, 11.2.2 and earlier, and 10.11.10 and earlier, indicating a widespread problem that has persisted across several major release branches. The core flaw lies in the improper validation of invite IDs during team creation processes, where the system fails to verify whether regular users have appropriate permissions to use specific invitation tokens. This vulnerability operates at the intersection of weak input validation and inadequate authorization checks, creating a pathway for unauthorized account registration that bypasses the intended access control mechanisms.
The technical implementation of this vulnerability stems from the absence of proper permission validation when processing invite IDs during team creation workflows. When users attempt to join a team using an invitation link, the system should verify that the invite ID belongs to the user's team or that the user possesses appropriate privileges to access that specific invitation. However, the flaw allows any user to submit an invite ID regardless of whether they should have access to it, effectively enabling privilege escalation through unauthorized account registration. This issue directly maps to CWE-285, which addresses improper authorization in software systems, and represents a classic case of insufficient access control validation. The vulnerability is particularly concerning because it allows regular users to gain access to teams they shouldn't be able to join, potentially compromising team confidentiality and data integrity.
The operational impact of this vulnerability extends beyond simple unauthorized access, creating significant risks for organizations relying on Mattermost for secure communication. Regular users could exploit this flaw to register accounts in teams they shouldn't have access to, potentially leading to information disclosure, unauthorized data access, and disruption of team collaboration workflows. The vulnerability is especially dangerous in environments where team membership controls are critical for maintaining security boundaries, such as in enterprise settings or regulated industries. Attackers could systematically test leaked invite IDs to gain access to multiple teams, effectively bypassing the intended security controls that protect team isolation and user privacy. This weakness undermines the fundamental security assumptions of the platform's invitation-based access control system.
Organizations should implement immediate mitigations to address this vulnerability, including applying the latest security patches provided by Mattermost as referenced in their advisory MMSA-2025-00565. System administrators should also consider implementing additional monitoring controls to detect unusual account registration patterns that might indicate exploitation attempts. The fix should involve strengthening the invite ID validation process to ensure that users can only register using invite IDs that are explicitly authorized for their team membership or that they have legitimate access rights to. This vulnerability demonstrates the critical importance of proper access control implementation and highlights the need for continuous security testing of core platform features. Security teams should also review their current access control policies and consider implementing additional layers of verification for team membership and invitation handling processes to prevent similar issues from occurring in other components of their communication infrastructure.