Mattermost fails to scope role_updated websocket events to authorized team and channel members
CVE-2026-3433

4.3MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
12 June 2026

What is CVE-2026-3433?

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 role_updated 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 notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616

Affected Version(s)

Mattermost 11.6.0 <= 11.6.1

Mattermost 11.5.0 <= 11.5.4

Mattermost 10.11.0 <= 10.11.15

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

0x7oda7123
.