Vulnerability · Published Aug 17, 2026 · Assigned by Mattermost
CVE-2026-9693Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite
Low 3.5
In plain English
A low-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).
Severity (CVSS 3.1)3.5Low
Exploit odds (30 days)0.3%top 80.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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 the team threads API.. Mattermost Advisory ID: MMSA-2026-00682
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 10.11.0 – through 10.11.2011.7.0 – through 11.7.5 |
Weakness: CWE-459 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
References
- MMSA-2026-00682 vendor-advisory