GO-2026-6547 Mattermost has an Incorrect Authorization issue in github.com/mattermost/mattermost-server

Mattermost has an Incorrect Authorization issue in github.com/mattermost/mattermost-server...

GO-2026-6484 Mattermost doesn't validate channel ownership of an existing subscription before applying edits in github.com/mattermost/mattermost-server

Mattermost doesn't validate channel ownership of an existing subscription before applying edits in github.com/mattermost/mattermost-server...

GO-2026-6480 Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler in github.com/mattermost/mattermost-server

Mattermost doesn't enforce administrator authorization on the setDefaultInstance call within the /gitlab connect command handler in github.com/mattermost/mattermost-server...

GO-2026-6481 Mattermost doesn't enforce bot-specific permission checks on the user active status endpoint in github.com/mattermost/mattermost-server

Mattermost doesn't enforce bot-specific permission checks on the user active status endpoint in github.com/mattermost/mattermost-server...

GO-2026-6483 Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret in github.com/mattermost/mattermost-server

Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret in github.com/mattermost/mattermost-server...

GO-2026-6482 Mattermost doesn't invalidate cached authentication state for active WebSocket connections during global session revocation in github.com/mattermost/mattermost-server

Mattermost doesn't invalidate cached authentication state for active WebSocket connections during global session revocation in github.com/mattermost/mattermost-server...

Mattermost Server 10.11.x < 10.11.23 / 11.7.x < 11.7.8 / 11.8.x < 11.8.5 / 11.9.x < 11.9.1 Incorrect Authorization (MMSA-2026-00702)

The version of Mattermost Server installed on the remote host is affected by a vulnerability as referenced in the MMSA-2026-00702 advisory. - Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to sanitize Team objects returned by the data retention team...

Mattermost Server 11.7.x < 11.7.11 / 11.8.x < 11.8.6 / 11.9.x < 11.9.2 / 11.10.x < 11.10.2 Multiple Vulnerabilities (MMSA-2026-00771, MMSA-2026-00775, MMSA-2026-00776)

The version of Mattermost Server installed on the remote host is affected by multiple vulnerabilities as referenced in the MMSA-2026-00771, MMSA-2026-00775, MMSA-2026-00776 advisories. - Mattermost versions 11.9.x = 11.9.1, 11.8.x = 11.8.5, 11.7.x = 11.7.10, 11.10.x = 11.10.1 fail to enforce a...

CVE-2026-86349 Mattermost Server Algorithmic DoS via Unbounded Markdown Block Nesting

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.8, 10.11.x = 10.11.22 fail to limit the nesting depth in the server-side Markdown parser which allows an authenticated attacker to cause a denial of service CPU resource exhaustion via a crafted post containing deeply nested...

CVE-2026-86349

Mattermost server versions 11.9.x ≤ 11.9.0, 11.8.x ≤ 11.8.4, 11.7.x ≤ 11.7.8, and 10.11.x ≤ 10.11.22 are affected by an algorithmic denial of service in the server-side Markdown parser. The root cause is a failure to limit nesting depth , allowing an authenticated attacker to exhaust CPU resource...

CVE-2026-86349 Mattermost Server Algorithmic DoS via Unbounded Markdown Block Nesting

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.8, 10.11.x = 10.11.22 fail to limit the nesting depth in the server-side Markdown parser which allows an authenticated attacker to cause a denial of service CPU resource exhaustion via a crafted post containing deeply nested...

CVE-2026-15814 Uploading a crafted image causes excessive memory allocation in the Mattermost Server

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to limit the amount of memory allocated when decoding uploaded image files which allows an authenticated user to cause excessive server memory consumption and potential denial of service via uploading a...

CVE-2026-15814

Mattermost Server versions 11.9.x ≤ 11.9.0, 11.8.x ≤ 11.8.4, 11.7.x ≤ 11.7.7, and 10.11.x ≤ 10.11.22 fail to limit the amount of memory allocated when decoding uploaded image files. An authenticated user can cause excessive server memory consumption and potential denial of service by uploading a ...

GO-2026-6282 Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations in github.com/mattermost/mattermost-server

Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations in github.com/mattermost/mattermost-server...

GO-2026-6279 Mattermost doesn't validate that a username returned during bot registration belongs to a bot account in github.com/mattermost/mattermost-server

Mattermost doesn't validate that a username returned during bot registration belongs to a bot account in github.com/mattermost/mattermost-server...

PT-2026-82031

Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations in github.com/mattermost/mattermost-server...

Mattermost Server 10.11.x < 10.11.22 / 11.7.x < 11.7.7 Multiple Vulnerabilities (MMSA-2026-00672, MMSA-2026-00675, MMSA-2026-00704)

The version of Mattermost Server installed on the remote host is affected by multiple vulnerabilities as referenced in the MMSA-2026-00672, MMSA-2026-00675, MMSA-2026-00704 advisories. - Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21 fail to prevent guest users from receiving Board Admin...

Mattermost Server 11.7.x < 11.7.7 / 11.8.x < 11.8.4 Incorrect Authorization (MMSA-2026-00718)

The version of Mattermost Server installed on the remote host is affected by a vulnerability as referenced in the MMSA-2026-00718 advisory. - Mattermost versions 11.7.x = 11.7.6, 11.8.x = 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belong...

Mattermost Server 10.11.x < 10.11.22 / 11.7.x < 11.7.7 / 11.8.x < 11.8.4 Multiple Vulnerabilities (MMSA-2026-00685, MMSA-2026-00686, MMSA-2026-00687, MMSA-2026-00691)

The version of Mattermost Server installed on the remote host is affected by multiple vulnerabilities as referenced in the MMSA-2026-00685, MMSA-2026-00686, MMSA-2026-00687, MMSA-2026-00691 advisories. - Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate...

CVE-2026-10819 Mattermost Server Denial of Service via Animated GIF Emoji Upload

Mattermost versions 11.6.x = 11.6.5, 10.11.x = 10.11.20, 11.8.x = 11.8.1, 11.7.x = 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom...