CVE-2026-9824: Remote cluster metadata enumeration via /share-channel autocomplete

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-13 · updated 2026-07-13
Weakness: CWE-862

Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to check the manage_shared_channels permission in the /share-channel autocomplete handler, which allows an authenticated user without that permission to enumerate configured remote cluster connection metadata via slash command autocomplete.. Mattermost Advisory ID: MMSA-2026-00676

Affected products

Mattermost: from 10.11.0 before 10.11.20; from 11.6.0 before 11.6.5; from 11.7.0 before 11.7.3 — fixed in 10.11.20, 11.6.5, 11.7.3

How to fix

Upgrade to a fixed version: Mattermost 10.11.20, 11.6.5, 11.7.3. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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