# CVE-2025-12689: Mattermost fails to check Websocket request for proper UTF-8 format potentially crashing Calls plug-in

Source: https://junglewise.ai/threats/cve-2025-12689-mattermost-fails-to-check-websocket-request-for-proper-utf-8  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-17  
License: CC BY 4.0 with a link back

CVE-2025-12689 · Severity: medium · CVSS 6.5 · Published 2025-12-17

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.

Technologies: [github.com/mattermost/mattermost-plugin-calls (Go)](https://junglewise.ai/threats/technologies/github-com-mattermost-mattermost-plugin-calls), [Mattermost Server](https://junglewise.ai/threats/technologies/server-public). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Mattermost](https://junglewise.ai/threats/vendors/mattermost).

## Quick answers

**Is CVE-2025-12689 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2025-12689 being exploited in the wild.

**How severe is CVE-2025-12689?** Medium severity, with a CVSS score of 6.5, published 17 December 2025.

**Which products and versions are affected?** github.com/mattermost/mattermost-plugin-calls (Go) SEMVER:introduced=0,fixed=1.11.0.

**Is there a fix for CVE-2025-12689?** Yes. github.com/mattermost/mattermost-plugin-calls (Go): upgrade to 1.11.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2025-12689?** Check whether you run github.com/mattermost/mattermost-plugin-calls (Go) or Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/mattermost/mattermost-plugin-calls (Go): upgrade to 1.11.0 or later

  ```sh
  go get github.com/mattermost/mattermost-plugin-calls@v1.11.0
  ```


## Affected products

- github.com/mattermost/mattermost-plugin-calls (Go) SEMVER:introduced=0,fixed=1.11.0
- Mattermost Server

## Identifiers

- CVE-2025-12689
- GHSA-j5vq-62gr-8v3r
- GO-2025-4255

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