CVE-2026-6342: mattermost server from 10.13.0 (inclusive), through 10.13.11 (inclusive), from 11.1.0 (inclusive), through 11.1.5…

Affected technology

mattermost server · from 10.13.0 (inclusive), through 10.13.11 (inclusive)
mattermost

mattermost server · from 11.1.0 (inclusive), through 11.1.5 (inclusive)
mattermost

mattermost server · from 11.3.0 (inclusive), through 11.3.4 (inclusive)
mattermost

Mattermost · 0 through 11.1.5, 0 through 10.13.11, 0 through 11.3.4
Mattermost

Description’s affected range: versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which

Component: Not specified by the source

Attack conditions (Vendor/CNA, CVSS 3.1): Network (remote) · Low privileges required · No user interaction required

What an attacker can do

Plugin users can create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Vendor/CNA’s CVSS 3.1 assessment (base score 4.3/10) rates confidentiality and availability impact as none; integrity impact as low.