CVE-2026-18799: 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) · Low privileges required · No user interaction required

What an attacker can do

An authenticated attacker with team admin privileges to force-add existing Mattermost users can their team and forge posts attributed to those users' identities via a crafted Slack export containing target users' email addresses. Vendor/CNA’s CVSS 3.1 assessment (base score 4.3/10) rates confidentiality and availability impact as none; integrity impact as low.