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CVE-2025-12559: Mattermost fails to sanitize team email addresses

November 27, 2025 (updated December 1, 2025)

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

References

  • github.com/advisories/GHSA-4g87-9x45-cx2h
  • github.com/mattermost/mattermost
  • github.com/mattermost/mattermost/commit/5d8719042c1807da59ac8a821624eb01152d8495
  • github.com/mattermost/mattermost/commit/649aee8fa9184ca59bd66022a33b8f8918e413aa
  • github.com/mattermost/mattermost/commit/7ccb62db7958abd6a4b21a06c5a4f5367a8f8b1f
  • github.com/mattermost/mattermost/commit/9f54e5cdc3aef412945ff0e6a58338f7b549bdda
  • github.com/mattermost/mattermost/commit/abbf01b9db45d1850eaf3701ea8362b910193ffd
  • github.com/mattermost/mattermost/pull/34110
  • mattermost.com/security-updates
  • nvd.nist.gov/vuln/detail/CVE-2025-12559

Code Behaviors & Features

Detect and mitigate CVE-2025-12559 with GitLab Dependency Scanning

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Affected versions

All versions starting from 10.5.0 before 10.5.13, all versions starting from 10.11.0 before 10.11.5, all versions starting from 10.12.0 before 10.12.2, all versions starting from 11.0.0 before 11.0.3

Fixed versions

  • 11.0.3
  • 10.12.2
  • 10.11.5
  • 10.5.13

Solution

Upgrade to versions 10.11.5, 10.12.2, 10.5.13, 11.0.3 or above.

Impact 4.3 MEDIUM

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

Learn more about CVSS

Weakness

  • CWE-200: Exposure of Sensitive Information to an Unauthorized Actor

Source file

go/github.com/mattermost/mattermost-server/CVE-2025-12559.yml

Spotted a mistake? Edit the file on GitLab.

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