CVE-2026-18223: Mattermost 11.10.0 through 11.10.0, 11.7.0 through 11.7.9, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5

Affected technology

Mattermost · 11.10.0 through 11.10.0, 11.7.0 through 11.7.9, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5
Mattermost

Description’s affected range: versions 11.10.x <= 11.10.0

Component: Not specified by the source

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

What an attacker can do

The source says mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link. Vendor/CNA’s CVSS 3.1 assessment (base score 5.0/10) rates confidentiality impact as high; integrity impact as low; availability impact as none.