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

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), Mattermost Server. Vendors: Go, 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
    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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