CVE-2026-3115

Guest users can view group member IDs without respecting view restrictions

CVSS 4.3 MEDIUMEPSS 0.2%CWE-863

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint.. Mattermost Advisory ID: MMSA-2026-00594

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected products

Mattermost · Mattermost

Want to know if your infrastructure is exposed to this?

Talk to TrueHacking →

References

https://mattermost.com/security-updates