CVE-2026-6046

MEDIUM

Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server

Title source: cna
STIX 2.1

Description

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00649
https://mattermost.com/security-updates

Scores

CVSS v3 5.3
EPSS 0.0019
EPSS Percentile 8.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-200
Status published
Products (9)
Mattermost/Mattermost 10.11.0 - 10.11.15
Mattermost/Mattermost 10.11.0 - 10.11.16
Mattermost/Mattermost 10.11.16
Mattermost/Mattermost 10.11.17
Mattermost/Mattermost 11.5.0 - 11.5.4
Mattermost/Mattermost 11.5.5
Mattermost/Mattermost 11.6.0 - 11.6.1
Mattermost/Mattermost 11.6.2
Mattermost/Mattermost 11.7.0
Published Jun 12, 2026
Tracked Since Jun 12, 2026