CVE-2026-4274
published 2026-03-26CVE-2026-4274: Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership…
medium5.4CVSS 3.1
AVNACLPRLUINSUCLILAN
Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574
Affected
13 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| github.com | mattermost_mattermost_server_v8 | >= 10.11.0-rc1 < 10.11.11 | 10.11.11 |
| github.com | mattermost_mattermost_server_v8 | >= 11.2.0-rc1 < 11.2.3 | 11.2.3 |
| github.com | mattermost_mattermost_server_v8 | >= 11.3.0-rc1 < 11.3.2 | 11.3.2 |
| github.com | mattermost_mattermost_server_v8 | >= 11.4.0-rc1 < 11.4.1 | 11.4.1 |
| github.com | mattermost_mattermost_server_v8 | >= 8.0.0-20260105080200-d27a2195068d < 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b |
| mattermost | mattermost | 10.11.0 – 10.11.10 | — |
| mattermost | mattermost | 11.2.0 – 11.2.2 | — |
| mattermost | mattermost | 11.3.0 – 11.3.1 | — |
| mattermost | mattermost | 11.4.0 – 11.4.0 | — |
| mattermost | mattermost_server | >= 10.11.0 < 10.11.11 | 10.11.11 |
| mattermost | mattermost_server | >= 11.2.0 < 11.2.3 | 11.2.3 |
| mattermost | mattermost_server | >= 11.3.0 < 11.3.2 | 11.3.2 |
| mattermost | mattermost_server | >= 11.4.0 < 11.4.1 | 11.4.1 |