CVE-2026-5163
published 2026-05-18CVE-2026-5163: 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…
medium6.5CVSS 3.1
AVNACLPRLUINSUCHINAN
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
Affected
5 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| github.com | mattermost_mattermost-server | >= 0 < 5.3.2-0.20260401090745-f4d1abe7e8f5 | 5.3.2-0.20260401090745-f4d1abe7e8f5 |
| github.com | mattermost_mattermost_server_v8 | >= 0 < 8.0.0-20260401090745-f4d1abe7e8f5 | 8.0.0-20260401090745-f4d1abe7e8f5 |
| github.com | mattermost_mattermost_server_v8 | >= 11.5.0 < 11.5.2 | 11.5.2 |
| mattermost | mattermost | 11.5.0 – 11.5.1 | — |
| mattermost | mattermost_server | >= 11.5.0 < 11.5.2 | 11.5.2 |