CVE-2026-5163

6.5 MEDIUM

Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authe...

Published: 2026-05-18 · Last updated: 2026-05-18

Severity and scoring

CVSS: 6.5 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CWE: CWE-862

Affected products

Vendor	Product
mattermost	mattermost_server

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

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-5163
[Vendor advisory]https://mattermost.com/security-updates

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