Mattermost Mattermost vulnerabilities

CVE-2026-2463 Medium · 4.3 CWE-862 Mar 16, 2026

Unauthorized access to invite ID during team creation

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

CVE-2026-2462 Medium · 6.6 CWE-863 Mar 16, 2026

Admin RCE via Malicious Plugin Upload on CI Test Instances

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to restrict plugin installation on CI test instances with default admin credentials which allows an unauthenticated attacker to achieve remote code execution and exfiltrate sensitive configuration data including AWS and SMTP credentials via uploading a malicious plugin after changing the import directory. Mattermost Advisory ID: MMSA-2025-00528

CVE-2026-2461 Medium · 4.3 CWE-639 Mar 16, 2026

Missing authorization check allows unauthorized modification of other users' comments on a board

Mattermost Plugins versions <=11.3 11.0.3 11.2.2 10.10.11.0 fail to implement authorisation checks on comment block modifications, which allows an authorised attacker with editor permission to modify comments created by other board members. Mattermost Advisory ID: MMSA-2025-00559

CVE-2026-2458 Medium · 4.3 CWE-862 Mar 16, 2026

Unauthorized channel enumeration in private teams after member removal

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate team membership when searching channels which allows a removed team member to enumerate all public channels within a private team via the channel search API endpoint.. Mattermost Advisory ID: MMSA-2025-00568

CVE-2026-2457 Medium · 4.3 CWE-346 Mar 16, 2026

WebSocket Message Spoofing via Permalink Embed Manipulation

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to sanitize client-supplied post metadata which allows an authenticated attacker to spoof permalink embeds impersonating other users via crafted PUT requests to the post update API endpoint.. Mattermost Advisory ID: MMSA-2025-00569

CVE-2026-2456 Medium · 5.7 CWE-789 Mar 16, 2026

Denial of Service via Unbounded Memory Allocation in Integration Actions

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 Mattermost fails to limit the size of responses from integration action endpoints, which allows an authenticated attacker to cause server memory exhaustion and denial of service via a malicious integration server that returns an arbitrarily large response when a user clicks an interactive message button.. Mattermost Advisory ID: MMSA-2026-00571

CVE-2026-26246 Medium · 4.3 CWE-789 Mar 16, 2026

Memory Exhaustion via Malformed PSD File Upload

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to bound memory allocation when processing PSD image files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted PSD file. Mattermost Advisory ID: MMSA-2026-00572

CVE-2026-25783 Medium · 4.3 CWE-1287 Mar 16, 2026

Denial of service via malformed User-Agent header in getBrowserVersion

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Mattermost Advisory ID: MMSA-2026-00586

CVE-2026-25780 Medium · 4.3 CWE-789 Mar 16, 2026

Memory Exhaustion via Malformed DOC File Upload

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to bound memory allocation when processing DOC files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted DOC file.. Mattermost Advisory ID: MMSA-2026-00581

CVE-2026-24458 High · 7.5 CWE-770 Mar 16, 2026

DoS attack via login attempts with multi-megabyte passwords

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587

CVE-2026-1628 Medium · 4.6 CWE-829 Mar 2, 2026

Mattermost allows external websites to open within the app, exposing preload functionality to non-trusted sites.

Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596

CVE-2026-1046 Medium · 6.5 CWE-939 Feb 16, 2026

Arbitrary application execution via unvalidated server-controlled URLs in Help menu

Mattermost Desktop App versions <=6.0 6.2.0 5.2.13.0 fail to validate help links which allows a malicious Mattermost server to execute arbitrary executables on a user’s system via the user clicking on certain items in the Help menu Mattermost Advisory ID: MMSA-2026-00577

CVE-2025-14573 Low · 2.7 CWE-862 Feb 16, 2026

Team Admin Bypass of Invite Permissions via allow_open_invite Field

Mattermost versions 10.11.x <= 10.11.9 fail to enforce invite permissions when updating team settings, which allows team administrators without proper permissions to bypass restrictions and add users to their team via API requests. Mattermost Advisory ID: MMSA-2025-00561

CVE-2025-14350 Medium · 4.3 CWE-862 Feb 16, 2026

Information disclosure via channel mentions in posts

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate team membership when processing channel mentions which allows authenticated users to determine the existence of teams and their URL names via posting channel shortlinks and observing the channel_mentions property in the API response. Mattermost Advisory ID: MMSA-2025-00563

CVE-2025-13821 Medium · 5.7 CWE-200 Feb 16, 2026

User profile update exposes password hash and MFA secrets

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560

CVE-2026-0999 Medium · 4.3 CWE-303 Feb 16, 2026

Authentication bypass via userID login when email and username login are disabled

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

CVE-2026-0998 Medium · 4.3 CWE-862 Feb 16, 2026

Mattermost Zoom Plugin allows unauthorized meeting creation and post modification via insufficient API access controls

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 and Mattermost Plugin Zoom versions <=1.11.0 fail to validate user identity and post ownership in the {{/api/v1/askPMI}} endpoint which allows unauthorized users to start Zoom meetings as any user and overwrite arbitrary posts via direct API calls with manipulated user IDs and post data.. Mattermost Advisory ID: MMSA-2025-00534

CVE-2026-0997 Medium · 4.3 CWE-863 Feb 16, 2026

Mattermost Zoom Plugin channel preference API lacks authorization checks

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 and Mattermost Plugin Zoom versions <=1.11.0 fail to validate the authenticated user when processing {{/plugins/zoom/api/v1/channel-preference}}, which allows any logged-in user to change Zoom meeting restrictions for arbitrary channels via crafted API requests.. Mattermost Advisory ID: MMSA-2025-00558

CVE-2026-22892 Medium · 4.3 CWE-863 Feb 13, 2026

Insufficient Authorization in Mattermost Jira Plugin Allows Unauthorized Access to Post Attachments

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to validate user permissions when creating Jira issues from Mattermost posts, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to via the /create-issue API endpoint by providing the post ID of an inaccessible post.. Mattermost Advisory ID: MMSA-2025-00550

CVE-2026-20796 Low · 3.1 CWE-367 Feb 13, 2026

Time-of-check time-of-use vulnerability in common teams API

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

CVE-2025-14435 Medium · 6.5 CWE-770 Jan 16, 2026

Application-Level DoS via infinite re-render loop in user profile handling

Mattermost versions 10.11.x <= 10.11.8, 11.1.x <= 11.1.1, 11.0.x <= 11.0.6 fail to prevent infinite re-renders on API errors which allows authenticated users to cause application-level DoS via triggering unbounded component re-render loops.

CVE-2025-14822 Medium · 6.5 CWE-770 Jan 16, 2026

DoS from quadratic complexity in model.ParseHashtags

Mattermost versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens

CVE-2025-64641 Medium · 4.1 CWE-863 Dec 24, 2025

Mattermost Jira plugin crafted action leaks Jira issue details

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fail to verify that post actions invoking /share-issue-publicly were created by the Jira plugin which allowed a malicious Mattermost user to exfiltrate Jira tickets when victim users interacted with affected posts

CVE-2025-13767 Medium · 4.3 CWE-863 Dec 24, 2025

Unauthorized Read Access to Private Channel Posts via Mattermost Jira Plugin

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.

CVE-2025-14273 High · 8.3 CWE-303 Dec 22, 2025

Mattermost Jira plugin user spoofing enables Jira request forgery.

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 with the Jira plugin enabled and Mattermost Jira plugin versions <=4.4.0 fail to enforce authentication and issue-key path restrictions in the Jira plugin, which allows an unauthenticated attacker who knows a valid user ID to issue authenticated GET and POST requests to the Jira server via crafted plugin payloads that spoof the user ID and inject arbitrary issue key paths. Mattermost Advisory ID: MMSA-2025-00555