EUVD-2026-60542

Mattermost versions 10.11.x = 10.11.20, 11.7.x = 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via t...

CVE-2026-9693 Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

Mattermost versions 10.11.x = 10.11.20, 11.7.x = 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via t...

CVE-2026-9693 Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

Mattermost versions 10.11.x = 10.11.20, 11.7.x = 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via t...

CVE-2026-16047 Board channel linking without read channel permission validation

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing...

CVE-2026-16047

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing...

CVE-2026-16047

Mattermost versions 11.7.x ≤ 11.7.6, 10.11.x ≤ 10.11.21, and 11.8.x ≤ 11.8.3 contain an authorization flaw in the board-to-channel linking functionality. The server fails to verify that the requesting user has read access to a target channel before associating a board with it. An authenticated us...

PT-2026-76661

Mattermost versions 11.7.x = 11.7.6, 10.11.x = 10.11.21, 11.8.x = 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing...

CVE-2026-9693: Incomplete Cleanup

Mattermost versions 10.11.x = 10.11.20, 11.7.x = 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via t...

PT-2026-76875

Name of the Vulnerable Software and Affected Versions Mattermost versions 10.11.0 through 10.11.20 Mattermost versions 11.7.0 through 11.7.5 Description The software fails to remove thread membership records when a user leaves or is removed from a team. This allows a user who is subsequently...

CVE-2026-48076

OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. The new-client booking flow in versions 1.0.1 and prior consists of three calls: bootstrap-challenge returns a 16-bit PoW challenge with difficulty=4 leading hex zeroes, bootstrap-verify...

CVE-2026-48076: Incorrect Authorization

OpenReception's appointment booking software provides an end-to-end encrypted appointment booking platform. The new-client booking flow in versions 1.0.1 and prior consists of three calls: bootstrap-challenge returns a 16-bit PoW challenge with difficulty=4 leading hex zeroes, bootstrap-verify...

Open WebUI: Private channel messages can be disclosed through cross-channel thread parent_id binding

SummaryA normal authenticated user can read the content of a message in a private channel they do not belong to. GET /api/v1/channels/id/messages/messageid/thread authorizes the caller against the URL channel, but the underlying thread lookup loads the thread parent by id and returns it without...

PYSEC-2026-3591 Open WebUI: Private channel messages can be disclosed through cross-channel thread parent_id binding

Summary A normal authenticated user can read the content of a message in a private channel they do not belong to. GET /api/v1/channels/id/messages/messageid/thread authorizes the caller against the URL channel, but the underlying thread lookup loads the thread parent by id and returns it without...

GHSA-73X5-H92W-XC2J Open WebUI: Private channel messages can be disclosed through cross-channel thread parent_id binding

Summary A normal authenticated user can read the content of a message in a private channel they do not belong to. GET /api/v1/channels/id/messages/messageid/thread authorizes the caller against the URL channel, but the underlying thread lookup loads the thread parent by id and returns it without...

Open WebUI: Private channel messages can be disclosed through cross-channel thread parent_id binding

Summary A normal authenticated user can read the content of a message in a private channel they do not belong to. GET /api/v1/channels/id/messages/messageid/thread authorizes the caller against the URL channel, but the underlying thread lookup loads the thread parent by id and returns it without...

PYSEC-2026-2720 Open WebUI Missing Access Check on Channel Members Endpoint for Standard Channels

Missing Access Check on Channel Members Endpoint for Standard Channels Affected Component Channel members listing endpoint: - backend/openwebui/routers/channels.py lines 445-507, getchannelmembersbyid Affected Versions Current main branch and likely all versions with the channels feature...

EUVD-2026-43312

Mattermost versions 11.7.x = 11.7.2, 11.6.x = 11.6.4, 10.11.x = 10.11.19 fail to verify that the channel referenced in an action cookie matches the channel of the target post, which allows an authenticated user without access to a private channel to trigger interactive post actions on posts in th...

CVE-2026-10106

Mattermost versions 11.7.x = 11.7.2, 11.6.x = 11.6.4, 10.11.x = 10.11.19 fail to verify that the channel referenced in an action cookie matches the channel of the target post, which allows an authenticated user without access to a private channel to trigger interactive post actions on posts in th...

CVE-2026-10106 Unauthorized users can trigger interactive post actions in private channels via action cookie channel mismatch in Mattermost

Mattermost versions 11.7.x = 11.7.2, 11.6.x = 11.6.4, 10.11.x = 10.11.19 fail to verify that the channel referenced in an action cookie matches the channel of the target post, which allows an authenticated user without access to a private channel to trigger interactive post actions on posts in th...

CVE-2026-10106

Mattermost vulnerable versions: 11.7.x ≤ 11.7.2, 11.6.x ≤ 11.6.4, and 10.11.x ≤ 10.11.19. The issue stems from failing to verify that the channel referenced in an action cookie matches the target post’s channel, enabling an authenticated user without access to a private channel to trigger interac...