Incorrect Authorization Affecting github.com/mattermost/mattermost/server/channels/app package, versions >=10.11.0-rc1 <10.11.14-rc1>=11.4.0-rc1 <11.4.4>=11.5.0-rc1 <11.5.2-rc2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-GOLANG-GITHUBCOMMATTERMOSTMATTERMOSTSERVERCHANNELSAPP-16755196
- published19 May 2026
- disclosed18 May 2026
- creditdaw10
Introduced: 18 May 2026
CVE-2026-28759 (opens in a new tab)How to fix?
Upgrade github.com/mattermost/mattermost/server/channels/app to version 10.11.14-rc1, 11.4.4, 11.5.2-rc2 or higher.
Overview
github.com/mattermost/mattermost/server/channels/app is a private-cloud Slack alternative
Affected versions of this package are vulnerable to Incorrect Authorization via the membership sync process. An attacker can remove users from any channel, including private channels, by sending crafted membership sync messages from a remote cluster that is not authorized to access the targeted channels.