CVE-2026-5163
MEDIUM
NVD
CVSS Score
6.5
Severity
MEDIUM
Published
May 18, 2026
Vendor
unknown
Description
Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645