CVE-2026-4273 Insufficient token rotation validation in remote cluster invite confirmation

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a craft...

CVE-2026-4273

Mattermost contains an insufficient validation flaw in remote cluster invite confirmation. Versions affected: 11.5.x ≤ 11.5.1 and 10.11.x ≤ 10.11.13. The RefreshedToken is not properly checked against the original invite token, allowing an authenticated attacker to bypass token rotation and reuse...

CVE-2026-4273 Insufficient token rotation validation in remote cluster invite confirmation

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a craft...

CVE-2026-3637 Mattermost fails to enforce create_post permission when editing posts

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to check the createpost channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and...

EUVD-2026-30741

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to check the createpost channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and...

CVE-2026-3637

Mattermost versions affected: 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, and 11.4.x

CVE-2026-3637 Mattermost fails to enforce create_post permission when editing posts

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to check the createpost channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and...

CVE-2026-3637

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to check the createpost channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and...

CVE-2026-3637 Mattermost fails to enforce create_post permission when editing posts

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to check the createpost channel permission during post edit operations which allows an authenticated attacker with revoked posting privileges to modify their existing posts via direct API requests to the post update and...

EUVD-2026-30737

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to...

CVE-2026-2325 Improper Input Validation in MS Teams Meetings API Handler

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to...

CVE-2026-2325

CVE-2026-2325 affects Mattermost versions 11.5.x up to 11.5.1, 10.11.x up to 10.11.13, and 11.4.x up to 11.4.3. The issue is an improper input validation where the start meeting API endpoint (/api/v1/meetings) does not limit the request body size, enabling an authenticated attacker to cause resou...

CVE-2026-2325

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to...

CVE-2026-28759 Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-28759

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-28759

Mattermost multiple releases (11.4.x <= 11.4.3, 11.5.x <= 11.5.1, 10.11.x

EUVD-2026-30738

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-28759 Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13, 11.4.x = 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel,...

CVE-2026-6334 OAuth authorization code client binding not enforced during token redemption in Mattermost

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermo...

CVE-2026-6334

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermo...