---
id: CVE-2024-1402
aliases:
  - GHSA-32h7-7j94-8fc2
  - BIT-mattermost-2024-1402
  - GO-2024-2541
title: Mattermost vulnerable to denial of service via large number of emoji reactions
summary: Mattermost vulnerable to denial of service via large number of emoji reactions
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'
vendor: mattermost
product: github.com/mattermost/mattermost/server/v8
ecosystem: go
affected:
  - github.com/mattermost/mattermost/server/v8 < 8.1.8
  - 'github.com/mattermost/mattermost/server/v8 >= 9.2.0, < 9.2.4'
  - 'github.com/mattermost/mattermost/server/v8 >= 9.1.0, < 9.1.5'
patched:
  - github.com/mattermost/mattermost/server/v8 8.1.8
  - github.com/mattermost/mattermost/server/v8 9.2.4
  - github.com/mattermost/mattermost/server/v8 9.1.5
published: '2024-02-09'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:05.197770614Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-32h7-7j94-8fc2'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2024-1402'
  - url: >-
      https://github.com/mattermost/mattermost/commit/64cb0ca8af2dbda1afcddd1604460591a4799b81
  - url: >-
      https://github.com/mattermost/mattermost/commit/6d2440de9fd774b67e65e3aac4ab8b6ef9aba2d8
  - url: >-
      https://github.com/mattermost/mattermost/commit/81190e2da128a6985914ea7023a69ac400513fc4
  - url: 'https://github.com/mattermost/mattermost'
  - url: 'https://mattermost.com/security-updates'
tags:
  - osv
  - go
epss: 0.00524
epssPercentile: 0.43453
ingestedAt: '2026-09-12T03:13:01.747Z'
---

## Overview

Mattermost fails to check if a custom emoji reaction exists when sending it to a post and to limit the amount of custom emojis allowed to be added in a post, allowing an attacker sending a huge amount of non-existent custom emojis in a post to crash the mobile app of a user seeing the post. Fetching posts with huge amounts of reactions results in Uncontrolled Resource Consumption.

## Affected packages

- `github.com/mattermost/mattermost/server/v8 < 8.1.8`
- `github.com/mattermost/mattermost/server/v8 >= 9.2.0, < 9.2.4`
- `github.com/mattermost/mattermost/server/v8 >= 9.1.0, < 9.1.5`

## Remediation

Upgrade to a patched release:

- `github.com/mattermost/mattermost/server/v8 8.1.8`
- `github.com/mattermost/mattermost/server/v8 9.2.4`
- `github.com/mattermost/mattermost/server/v8 9.1.5`