Mattermost fails to properly validate post props

Exploitation

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

CVSS

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

EPSS

• CVE-2025-20088: 0.58% estimated exploitation activity in the next 30 days; percentile 47.98 (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 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate post props which allows a malicious authenticated user to cause a crash via a malicious post.

Published by the source

15 Jan 2025, 18:30 UTC

Last modified by the source

17 Jan 2025, 15:50 UTC

Source last checked

26 Oct 2026, 15:08 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-45v9-w9fh-33j6

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# Patch Next advisory brief: CVE-2025-20088

Advisory: Mattermost fails to properly validate post props
IDs: CVE-2025-20088, GHSA-45v9-w9fh-33j6
Record: https://patchnext.com/advisories/cve-2025-20088 (revision 1, source checked 26 Oct 2026, 15:08 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
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 10.2.1, 10.1.4, 10.0.4, 9.11.6, 8.0.0-20241127161322-25ff7a3779a5. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mattermost/mattermost/server/v8: affected >= 10.2.0, < 10.2.1; >= 10.1.0, <= 10.1.3; >= 10.0.0, <= 10.0.3; >= 9.11.0, <= 9.11.5; < 8.0.0-20241127161322-25ff7a3779a5; fixed in 10.0.4, 8.0.0-20241127161322-25ff7a3779a5, 10.1.4, 9.11.6, 10.2.1

## 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-45v9-w9fh-33j6 (GitHub-reviewed advisory GHSA-45v9-w9fh-33j6 lists affected ranges: Go github.com/mattermost/mattermost/server/v8 >=10.2.0 =10.1.0 =10.0.0 =9.11.0 =0 <8.0.0-20241127161322-25ff7a3779a5)

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