Low severity · published Aug 17, 2026
CVE-2026-9693
Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite
3.5
CVSS
0.3%
EPSS
No
On KEV
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
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 19% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
10.11.0 through 10.11.20; 11.7.0 through 11.7.5 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.21; 11.7.0 before 11.7.6 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9693
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-9693
Vendor Advisory
https://mattermost.com/security-updates
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