EUVD-2026-43307

Mattermost versions 11.7.x = 11.7.2, 11.6.x = 11.6.4, 10.11.x = 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing...

CVE-2026-9708

Mattermost vulnerable versions (11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x

CVE-2026-9571

Mattermost CVE-2026-9571 affects versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, and 10.11.x

EUVD-2026-38250

Mattermost versions 11.7.x = 11.7.0, 11.6.x = 11.6.2, 11.5.x = 11.5.5, 10.11.x = 10.11.17 Fail to validate channel ownership of an existing subscription before applying edits which allows an authenticated attacker to hijack subscriptions from channels they have no access to via a crafted PUT...

CVE-2026-6062 IDOR in Jira plugin subscription edit endpoint

Mattermost versions 11.7.x = 11.7.0, 11.6.x = 11.6.2, 11.5.x = 11.5.5, 10.11.x = 10.11.17 Fail to validate channel ownership of an existing subscription before applying edits which allows an authenticated attacker to hijack subscriptions from channels they have no access to via a crafted PUT...

EUVD-2026-38249

Mattermost versions 11.7.x = 11.7.0, 11.6.x = 11.6.2, 11.5.x = 11.5.5, 10.11.x = 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt the Jira integration via POST to /ac/installed during the...

CVE-2026-9162 Global session revocation does not invalidate active WebSocket connections

Mattermost versions 11.7.x = 11.7.0, 11.6.x = 11.6.2, 11.5.x = 11.5.5, 10.11.x = 10.11.17 fail to invalidate cached authentication state for active WebSocket connections during global session revocation, which allows a user with an existing WebSocket connection to remain authenticated and continu...

CVE-2026-9162 Global session revocation does not invalidate active WebSocket connections

Mattermost versions 11.7.x = 11.7.0, 11.6.x = 11.6.2, 11.5.x = 11.5.5, 10.11.x = 10.11.17 fail to invalidate cached authentication state for active WebSocket connections during global session revocation, which allows a user with an existing WebSocket connection to remain authenticated and continu...

CVE-2026-6961

Mattermost versions 11.6.x = 11.6.1, 11.5.x = 11.5.4, 10.11.x = 10.11.15, 10.11.x = 10.11.16 Mattermost fails to sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations...

CVE-2026-6961 CVE-2026-6961: Path traversal via unsanitized FileInfo.Name in Mattermost federation sync

Mattermost versions 11.6.x = 11.6.1, 11.5.x = 11.5.4, 10.11.x = 10.11.15, 10.11.x = 10.11.16 Mattermost fails to sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations...

CVE-2026-6961

Mattermost CVE-2026-6961 affects Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, and 10.11.x <= 10.11.15/10.11.x

CVE-2026-7387 Mattermost group syncable endpoints allow privilege escalation via scheme_admin

Mattermost versions 11.6.x = 11.6.1, 11.5.x = 11.5.4, 10.11.x = 10.11.15, 10.11.x = 10.11.16 Mattermost fails to require role-management authorization when setting the schemeadmin flag on group syncable link and patch endpoints, which allows a user with group-link permissions to escalate themselv...

EUVD-2026-36498

Mattermost versions 11.6.x = 11.6.1, 11.5.x = 11.5.4, 10.11.x = 10.11.15, 10.11.x = 10.11.16 fail to restrict roleupdated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change...

CVE-2026-3495

Mattermost versions 11.5.x = 11.5.1, 10.11.x = 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code via injecting some JS as part of those...

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-2026-28735

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 the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL...

GHSA-RMVV-8V8W-RF7X Mattermost doesn't validate user-supplied input in API request handlers

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-2026-4915 Server panic via outgoing webhook responses

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 filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service server process termination via a crafted webhook...

EUVD-2026-31465

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 the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL...

CVE-2026-28735

Mattermost versions 10.11.x up to 10.11.14, 11.4.x up to 11.4.4, 11.5.x up to 11.5.3, and 11.6.x up to 11.6.0 fail to validate the OAuth token scope on the callback, enabling an authenticated Mattermost user to gain access to private repositories by modifying the scope parameter in the GitHub aut...