Mattermost allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL

Exploitation

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

CVSS

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

EPSS

• CVE-2025-55073: 0.20% estimated exploitation activity in the next 30 days; percentile 9.36 (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 10.11.x <= 10.11.3, 10.5.x <= 10.5.11, 10.12.x <= 10.12.0 fail to validate the relationship between the post being updated and the MSTeams plugin OAuth flow which allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL.

Published by the source

14 Nov 2025, 09:30 UTC

Last modified by the source

17 Nov 2025, 17:58 UTC

Source last checked

26 Oct 2026, 15:13 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ff85-qw3h-g9vp

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# Patch Next advisory brief: CVE-2025-55073

Advisory: Mattermost allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL
IDs: CVE-2025-55073, GHSA-ff85-qw3h-g9vp
Record: https://patchnext.com/advisories/cve-2025-55073 (revision 1, source checked 26 Oct 2026, 15:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
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 8.0.0-20250929212932-a41db04d2746; github.com/mattermost/mattermost-server 10.12.1, 10.11.4, 10.5.12. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected < 8.0.0-20250929212932-a41db04d2746; fixed in 8.0.0-20250929212932-a41db04d2746
- Go github.com/mattermost/mattermost-server: affected >= 10.11.0, < 10.11.4; >= 10.5.0, < 10.5.12; >= 10.12.0, < 10.12.1; fixed in 10.11.4, 10.5.12, 10.12.1

## 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-ff85-qw3h-g9vp (GitHub-reviewed advisory GHSA-ff85-qw3h-g9vp lists affected ranges: Go github.com/mattermost/mattermost-server >=10.11.0 =10.5.0 =10.12.0 =0 <8.0.0-20250929212932-a41db04d2746)

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