CVE-2026-6046 MEDIUM

CVE-2026-6046: Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server

Vendor Mattermost
Product Mattermost
Weakness CWE-200 · Info exposure
Published June 12, 2026
Last update June 12, 2026
View on NVD All CVEs

CVSS base score

5.3/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality High
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

June 12, 2026 CVE published
June 12, 2026 Record updated