Mattermost Fails to Verify User's Permissions When Accessing Groups

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2025-2527: 0.31% estimated exploitation activity in the next 30 days; percentile 24.41 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Mattermost versions 10.5.x <= 10.5.2, 9.11.x <= 9.11.11 failed to properly verify a user's permissions when accessing groups, which allows an attacker to view group information via an API request.

Published by the source

15 May 2025, 18:31 UTC

Last modified by the source

17 May 2025, 14:02 UTC

Source last checked

26 Oct 2026, 15:09 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h356-3mfw-x368

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# Patch Next advisory brief: CVE-2025-2527

Advisory: Mattermost Fails to Verify User's Permissions When Accessing Groups
IDs: CVE-2025-2527, GHSA-h356-3mfw-x368
Record: https://patchnext.com/advisories/cve-2025-2527 (revision 1, source checked 26 Oct 2026, 15:09 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/mattermost/mattermost/server/v8 10.5.3, 9.11.12, 8.0.0-20250411064244-844447fbd57c. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected >= 10.5.0, <= 10.5.2; >= 9.11.0, <= 9.11.11; < 8.0.0-20250411064244-844447fbd57c; fixed in 9.11.12, 8.0.0-20250411064244-844447fbd57c, 10.5.3

## Suggested inspection (read-only)
- Go github.com/mattermost/mattermost/server/v8: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/mattermost/mattermost/server/v8.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-h356-3mfw-x368 (GitHub-reviewed advisory GHSA-h356-3mfw-x368 lists affected ranges: Go github.com/mattermost/mattermost/server/v8 >=10.5.0 =9.11.0 =0 <8.0.0-20250411064244-844447fbd57c)

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