Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to filter nil elements from outgoing webhook attachment payloads before processing, which allows an authenticated user to cause a denial of service (server process termination) via a crafted webhook callback response containing a null attachment entry.. Mattermost Advisory ID: MMSA-2026-00641
Exploitability
AV:NAC:LPR:LUI:NScope
S:UImpact
C:NI:NA:H6.5/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HOther