---
id: CVE-2025-20086
aliases:
  - GHSA-5m7j-6gc4-ff5g
  - GO-2025-3392
title: Mattermost fails to properly validate post props
summary: Mattermost fails to properly validate post props
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
vendor: mattermost
product: github.com/mattermost/mattermost/server/v8
ecosystem: go
affected:
  - 'github.com/mattermost/mattermost/server/v8 >= 10.2.0, < 10.2.1'
  - 'github.com/mattermost/mattermost/server/v8 >= 10.1.0, < 10.1.4'
  - 'github.com/mattermost/mattermost/server/v8 >= 10.0.0, < 10.0.4'
  - 'github.com/mattermost/mattermost/server/v8 >= 9.11.0, < 9.11.6'
  - >-
    github.com/mattermost/mattermost/server/v8 <
    8.0.0-20241127161322-25ff7a3779a5
patched:
  - github.com/mattermost/mattermost/server/v8 10.2.1
  - github.com/mattermost/mattermost/server/v8 10.1.4
  - github.com/mattermost/mattermost/server/v8 10.0.4
  - github.com/mattermost/mattermost/server/v8 9.11.6
  - github.com/mattermost/mattermost/server/v8 8.0.0-20241127161322-25ff7a3779a5
published: '2025-01-15'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:21.861419050Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-5m7j-6gc4-ff5g'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2025-20086'
  - url: 'https://github.com/mattermost/mattermost'
  - url: 'https://mattermost.com/security-updates'
  - url: 'https://pkg.go.dev/vuln/GO-2025-3392'
tags:
  - osv
  - go
epss: 0.00428
epssPercentile: 0.34349
ingestedAt: '2026-09-12T03:13:01.756Z'
---

## Overview

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.

## Affected packages

- `github.com/mattermost/mattermost/server/v8 >= 10.2.0, < 10.2.1`
- `github.com/mattermost/mattermost/server/v8 >= 10.1.0, < 10.1.4`
- `github.com/mattermost/mattermost/server/v8 >= 10.0.0, < 10.0.4`
- `github.com/mattermost/mattermost/server/v8 >= 9.11.0, < 9.11.6`
- `github.com/mattermost/mattermost/server/v8 < 8.0.0-20241127161322-25ff7a3779a5`

## Remediation

Upgrade to a patched release:

- `github.com/mattermost/mattermost/server/v8 10.2.1`
- `github.com/mattermost/mattermost/server/v8 10.1.4`
- `github.com/mattermost/mattermost/server/v8 10.0.4`
- `github.com/mattermost/mattermost/server/v8 9.11.6`
- `github.com/mattermost/mattermost/server/v8 8.0.0-20241127161322-25ff7a3779a5`