CVE-2026-19867: Mattermost 11.10.0 through 11.10.0, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5, 11.7.0 through 11.7.10

Affected technology

Mattermost · 11.10.0 through 11.10.0, 11.9.0 through 11.9.1, 11.8.0 through 11.8.5, 11.7.0 through 11.7.10
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 user can degrade post-processing latency and consume excessive CPU on behalf of other members of any channel they share via storing an oversized notify_props.mention_keys list on their own profile. Vendor/CNA’s CVSS 3.1 assessment (base score 4.3/10) rates confidentiality and integrity impact as none; availability impact as low.