Missing authorization check in AI message rewrite endpoint allows access to private thread content
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.5epss 0.2%
exploitation probability
0.2%top 89% of all CVEs
observed exploitation
nono source reports it
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
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Affected products
Mattermost · MattermostReferences
https://mattermost.com/security-updates