CVE-2026-4635

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

CVE-2026-4646

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID:...

CVE-2026-4635 Persistent notification timing attack causing server denial of service

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

CVE-2026-4635 Persistent notification timing attack causing server denial of service

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

CVE-2026-4635

Mattermost (versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x

EUVD-2026-31431

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

CVE-2026-4635

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

CVE-2026-4635 Persistent notification timing attack causing server denial of service

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting...

EUVD-2026-31429

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs...

CVE-2026-3473

CVE-2026-3473 affects Mattermost prior to fixed versions: 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, and 10.11.x

CVE-2026-3473 Improper file ownership validation in the Boards API allows unauthorised file access

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs...

CVE-2026-3473

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs...

CVE-2026-3473 Improper file ownership validation in the Boards API allows unauthorised file access

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs...

CVE-2026-4646 Insufficient input validation in GitHub plugin API causes denial of service

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID:...

EUVD-2026-31430

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID:...

CVE-2026-4646

Mattermost has an input-validation flaw in the API request handlers used by the PR details endpoint. Affected versions are 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, and 10.11.x

CVE-2026-4646

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint.. Mattermost Advisory ID:...

CVE-2026-3636

Mattermost CVE-2026-3636 affects versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, and 10.11.x

CVE-2026-3636

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to sanitize team member data when returned via API to users without elevated permissions which allows a user without permissions to get data about team members roles via invoking various team API...

EUVD-2026-31428

Mattermost versions 11.6.x = 11.6.0, 11.5.x = 11.5.3, 11.4.x = 11.4.4, 10.11.x = 10.11.14 fail to sanitize team member data when returned via API to users without elevated permissions which allows a user without permissions to get data about team members roles via invoking various team API...