CVE-2026-6347: Mattermost Calls plugin information disclosure in support packets

CVE-2026-6347 · Severity: high · CVSS 7.6 · Published 2026-05-18

Mattermost, a popular collaboration and messaging platform, contains a vulnerability in its 'Calls' plugin that fails to properly hide sensitive information. An attacker with administrative access to system support logs (support packets) can view TURN server credentials in plain text. This could allow an unauthorized party to hijack video/audio calling infrastructure or gain deeper access to the communication environment.

Technologies: github.com/mattermost/mattermost-plugin-calls (Go), github.com/mattermost/mattermost-server (Go), Mattermost Server. Vendors: Go, Mattermost.

Quick answers

Is CVE-2026-6347 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-6347 being exploited in the wild.
How severe is CVE-2026-6347?
High severity, with a CVSS score of 7.6, published 18 May 2026.
Which products and versions are affected?
github.com/mattermost/mattermost-plugin-calls (Go) SEMVER:introduced=0,fixed=1.12.0-rc2; github.com/mattermost/mattermost-server (Go) SEMVER:introduced=10.11.0+incompatible,fixed=10.11.14+incompatible,introduced=11.4.0+incompatible,fixed=11.4.4+incompatible,introduced=11.5.0+incompatible,fixed=11.5.2+incompatible, SEMVER:introduced=11.5.0,fixed=11.5.2; Mattermost Calls Plugin < 1.12.0-rc2; Mattermost Server 11.5.0 - 11.5.1, 10.11.0 - 10.11.13, 11.4.0 - 11.4.3, 11.5.0 to 11.5.1, 11.4.0 to 11.4.3, 10.11.0 to 10.11.13.
Is there a fix for CVE-2026-6347?
Yes. github.com/mattermost/mattermost-plugin-calls (Go): upgrade to 1.12.0-rc2 or later; github.com/mattermost/mattermost-server (Go): upgrade to 11.5.2, 11.5.2+incompatible or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-6347 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-6347?
Check whether you run github.com/mattermost/mattermost-plugin-calls (Go), github.com/mattermost/mattermost-server (Go), Mattermost Calls Plugin or one of the others listed 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 1.12.0-rc2 or later
    go get github.com/mattermost/mattermost-plugin-calls@v1.12.0-rc2
  • github.com/mattermost/mattermost-server (Go): upgrade to 11.5.2, 11.5.2+incompatible or later
    go get github.com/mattermost/mattermost-server@v11.5.2+incompatible

Technical details

A sensitive information disclosure vulnerability (CWE-200) exists in the Mattermost Calls plugin due to insufficient sanitization of configuration fields. When a support packet is generated for troubleshooting, the plugin includes the 'ICEServersConfigs' and 'TURNStaticAuthSecret' fields in plaintext within the exported configuration. An attacker with high privileges (sufficient to access or generate support packets) can extract TURN server usernames and passwords. This vulnerability is addressed by marking these configuration keys as 'secret' in the plugin metadata to ensure they are redacted during exports. Patches are available in Mattermost Server versions 11.5.2, 10.11.14, and 11.4.4, and Calls plugin version 1.12.0-rc2.

Affected products

  • Mattermost Mattermost Server 11.5.0 - 11.5.1, 10.11.0 - 10.11.13, 11.4.0 - 11.4.3
  • Mattermost Mattermost Calls Plugin < 1.12.0-rc2

Identifiers

  • CVE-2026-6347
  • GHSA-82j6-4fq7-fx62
  • GO-2026-5238

Timeline

  • 2026-05-18: disclosed
  • 2026-05-18: advisory
  • 2026-06-01: patched

References

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