GitHub Advisoryadvisory · Go
GHSA-g7fp-cqj5-x8hf Mattermost has an Incorrect Authorization issue
MEDIUM
Official page ↗
- Aliases
- CVE-2026-4274
- Ecosystem
- Go
- Packages
- github.com/mattermost/mattermost/server/v8
- Severity
- Moderate
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
- Weaknesses
- CWE-863
- Reviewed
- 2026-03-31
Affected packages
• Go github.com/mattermost/mattermost/server/v8: >= 11.4.0-rc1, < 11.4.1 → fixed in 11.4.1
• Go github.com/mattermost/mattermost/server/v8: >= 11.3.0-rc1, < 11.3.2 → fixed in 11.3.2
• Go github.com/mattermost/mattermost/server/v8: >= 11.2.0-rc1, < 11.2.3 → fixed in 11.2.3
• Go github.com/mattermost/mattermost/server/v8: >= 10.11.0-rc1, < 10.11.11 → fixed in 10.11.11
• Go github.com/mattermost/mattermost/server/v8: >= 8.0.0-20260105080200-d27a2195068d, < 8.0.0-20260217110922-b7d4a1f1f59b → fixed in 8.0.0-20260217110922-b7d4a1f1f59b
Description
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
Related
Alias · CVE (1)
- CVE-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… vulnerability
Weakness · CWE (1)
- CWE-863 Incorrect Authorization weakness