CVE-2025-12559: Information Disclosure in Common Teams API

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-11-27 · updated 2026-10-19
Weakness: CWE-200

Description

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

Affected products

Mattermost: from 10.5.0 before 10.5.13; from 10.11.0 before 10.11.5; from 10.12.0 before 10.12.2; from 11.0.0 before 11.0.3 — fixed in 10.11.5, 10.12.2, 10.5.13, 11.0.3

How to fix

Upgrade to a fixed version: Mattermost 10.11.5, 10.12.2, 10.5.13, 11.0.3. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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