Mattermost Fails to Sanitize File Names

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:N/I:L/A:N

EPSS

• CVE-2025-6465: 0.77% estimated exploitation activity in the next 30 days; percentile 55.50 (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 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 10.10.x <= 10.10.0, 10.9.x <= 10.9.3 fail to sanitize file names which allows users with file upload permission to overwrite file attachment thumbnails via path traversal in file streaming APIs.

Published by the source

21 Aug 2025, 18:31 UTC

Last modified by the source

29 Aug 2025, 21:00 UTC

Source last checked

26 Oct 2026, 15:10 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pj6f-rc94-gw53

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# Patch Next advisory brief: CVE-2025-6465

Advisory: Mattermost Fails to Sanitize File Names
IDs: CVE-2025-6465, GHSA-pj6f-rc94-gw53
Record: https://patchnext.com/advisories/cve-2025-6465 (revision 1, source checked 26 Oct 2026, 15:10 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 8.0.0-20250708173752-d6b35c41f0ae5; github.com/mattermost/mattermost-server 10.10.1, 10.9.4, 10.8.4, 10.5.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected < 8.0.0-20250708173752-d6b35c41f0ae5; fixed in 8.0.0-20250708173752-d6b35c41f0ae5
- Go github.com/mattermost/mattermost-server: affected >= 10.8.0, <= 10.8.3; >= 10.5.0, <= 10.5.8; >= 10.9.0, <= 10.9.3; >= 10.10.0, <= 10.10.0; fixed in 10.9.4, 10.5.9, 10.10.1, 10.8.4

## Suggested inspection (read-only)
- Go github.com/mattermost/mattermost/server/v8: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server: 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, github.com/mattermost/mattermost-server.
- 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-pj6f-rc94-gw53 (GitHub-reviewed advisory GHSA-pj6f-rc94-gw53 lists affected ranges: Go github.com/mattermost/mattermost-server >=10.8.0 =10.5.0 =10.9.0 =10.10.0 =0 <8.0.0-20250708173752-d6b35c41f0ae5)

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