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Medium, CVSS 6.8

Mattermost Fails to Validate Remote Cluster Upload Sessions

CVE-2025-49222GHSA-q453-638c-h4mr

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • 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/v6

    Affected
    <= 5.7.2
    Fixed in
    no fixed version recorded

  • Go github.com/mattermost/mattermost-server

    Affected
    >= 10.8.0, <= 10.8.3>= 10.5.0, <= 10.5.8>= 9.11.0, <= 9.11.17>= 10.9.0, <= 10.9.2>= 10.10.0, <= 10.10.0
    Fixed in
    10.5.9, 10.10.1, 9.11.18, 10.8.4, 10.9.3

  • Go github.com/mattermost/mattermost-server/v5

    Affected
    <= 5.39.3
    Fixed in
    no fixed version recorded

Sources

  • GitHub Advisory Database and maintainer security advisories on GitHub

    GitHub-reviewed advisory GHSA-q453-638c-h4mr lists affected ranges: Go github.com/mattermost/mattermost-server >=10.8.0 =10.5.0 =9.11.0 =10.9.0 =10.10.0 =0 =0 =0 <=5.7.2

    VerifiedObserved Structured GitHub Advisory Database record (type=reviewed) from the GitHub REST API.

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.8 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N
EPSS
  • CVE-2025-49222: 0.30% estimated exploitation activity in the next 30 days; percentile 22.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2, 10.10.x <= 10.10.0 fail to validate upload types in remote cluster upload sessions which allows a system admin to upload non-attachment file types via shared channels that could potentially be placed in arbitrary filesystem directories.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-q453-638c-h4mr

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-49222

Advisory: Mattermost Fails to Validate Remote Cluster Upload Sessions
IDs: CVE-2025-49222, GHSA-q453-638c-h4mr
Record: https://patchnext.com/advisories/cve-2025-49222 (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 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/mattermost/mattermost/server/v8 8.0.0-20250708173752-d6b35c41f0ae5; github.com/mattermost/mattermost-server 10.10.1, 10.9.3, 10.8.4, 10.5.9, 9.11.18. 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/v6: affected <= 5.7.2
- Go github.com/mattermost/mattermost-server: affected >= 10.8.0, <= 10.8.3; >= 10.5.0, <= 10.5.8; >= 9.11.0, <= 9.11.17; >= 10.9.0, <= 10.9.2; >= 10.10.0, <= 10.10.0; fixed in 10.5.9, 10.10.1, 9.11.18, 10.8.4, 10.9.3
- Go github.com/mattermost/mattermost-server/v5: affected <= 5.39.3

## 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/v6: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server: check the installed version with your package manager.
- Go github.com/mattermost/mattermost-server/v5: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## 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/v6, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5.
- 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-q453-638c-h4mr (GitHub-reviewed advisory GHSA-q453-638c-h4mr lists affected ranges: Go github.com/mattermost/mattermost-server >=10.8.0 =10.5.0 =9.11.0 =10.9.0 =10.10.0 =0 =0 =0 <=5.7.2)

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