MEDIUMCVSS 6.4EPSS 0.2%

CVE-2026-6062

Mattermost doesn't validate channel ownership of an existing subscription before applying edits

Published: 2026-06-22
Modified: 2026-09-15
EPSS percentile: 15%
Aliases: GHSA-mxq2-5jpg-7474
Sources: github-advisory

Summary

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 Fail to validate channel ownership of an existing subscription before applying edits which allows an authenticated attacker to hijack subscriptions from channels they have no access to via a crafted PUT request to the subscription edit endpoint.. Mattermost Advisory ID: MMSA-2026-00650

Affected packages

Ecosystem	Package	Affected versions	Fixed versions
Go	github.com/mattermost/mattermost-server	—	11.7.1, 11.6.3, 11.5.6, 10.11.18

Remediation: Upgrade to 11.7.1 or later.

References

https://github.com/advisories/GHSA-mxq2-5jpg-7474

Includes data from the GitHub Advisory Database, licensed under CC-BY 4.0.

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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.