CVE-2026-9708 — Incoming webhook user attribution via unvalidated webhook owner

CVE-2026-9708

Incoming webhook user attribution via unvalidated webhook owner PUBLISHED

Description (CNA)

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

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.7.0 through 11.7.2; affected 11.6.0 through 11.6.4; affected 10.11.0 through 10.11.19; unaffected 11.8.0; unaffected 11.7.3; unaffected 11.6.5; unaffected 10.11.20

CWE

CWE-639

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.