Incorrect Authorization

Overview Affected versions of this package are vulnerable to Incorrect Authorization via the membership sync process. An attacker can remove users from any channel, including private channels, by sending crafted membership sync messages from a remote cluster that is not authorized to access the...

Authentication Bypass by Primary Weakness

Overview github.com/mattermost/mattermost/server/channels/app is a private-cloud Slack alternative Affected versions of this package are vulnerable to Authentication Bypass by Primary Weakness in the OAuth authorization code redemption process. An attacker can gain unauthorized access to resource...

Mattermost doesn't verify channel membership when processing AI-assisted message rewrites

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

GHSA-8R89-8W26-CQ32 Mattermost doesn't verify channel membership when processing AI-assisted message rewrites

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

GHSA-8H9W-W78C-VVR3 Mattermost does not verify remote cluster channel access when processing shared channel membership removals

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-2026-5163

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

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,...

EUVD-2026-30753

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163

Mattermost versions 11.5.x = 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite...

CVE-2026-5163

Mattermost 11.5.x prior to 11.5.2 (up to 11.5.1 affected) fails to verify channel membership when processing AI-assisted message rewrites, allowing an authenticated user to read content from threads in private channels and direct messages they should not access via a crafted request to the post r...

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 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

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,...

Mattermost 安全漏洞

Mattermost is an open-source collaboration platform developed by the American company Mattermost. Versions of Mattermost 11.5.1 and earlier, including 11.5.x, have security vulnerabilities. These vulnerabilities stem from the lack of verification of channel members when processing AI-assisted...

Mattermost 安全漏洞

Mattermost is an open-source collaboration platform developed by the American company Mattermost. Vulnerabilities exist in Mattermost versions 11.5.1 and earlier of the 11.5.x series, as well as versions 10.11.13 and earlier of the 10.11.x series, and 11.4.3 and earlier of the 11.4.x series. Thes...

PT-2026-41655

Name of the Vulnerable Software and Affected Versions Mattermost versions 11.5.x through 11.5.1 Description An issue exists where channel membership is not verified during the processing of AI-assisted message rewrites. This allows an authenticated attacker to read the content of threads in priva...

CVE-2026-44571

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.8.6, in standard channels i.e., channels whose channel.type is neither group nor dm, the endpoint POST /api/v1/channels/channelid/messages/messageid/update can be accessed with read...

CVE-2026-44571 Open WebUI: Improper Authorization in Standard Channels Allows Message Updates with Read Permission

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.8.6, in standard channels i.e., channels whose channel.type is neither group nor dm, the endpoint POST /api/v1/channels/channelid/messages/messageid/update can be accessed with read...