CVE-2026-9708

MEDIUM

Mattermost - Incoming Webhook User Attribution via Unvalidated Webhook Owner

Title source: rule
STIX 2.1

Description

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming webhook user has access to the target team or channel, which allows a requester with webhook management permissions to create posts or direct messages attributed to another user via crafted incoming webhook configuration and payloads.. Mattermost Advisory ID: MMSA-2026-00683

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00683
https://mattermost.com/security-updates

Scores

CVSS v3 4.9
EPSS 0.0021
EPSS Percentile 11.2%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-639
Status published
Products (8)
Mattermost/Mattermost 10.11.0 - 10.11.19
Mattermost/Mattermost 10.11.20
Mattermost/Mattermost 11.6.0 - 11.6.4
Mattermost/Mattermost 11.6.5
Mattermost/Mattermost 11.7.0 - 11.7.2
Mattermost/Mattermost 11.7.3
Mattermost/Mattermost 11.8.0
mattermost/mattermost_server 10.11.0 - 10.11.20
Published Jul 13, 2026
Tracked Since Jul 13, 2026