Moderate severityNVD Advisory· Published Mar 26, 2026· Updated Mar 26, 2026
Insufficient authorization in shared channel membership sync grants team-level access instead of channel-level access
CVE-2026-4274
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
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
github.com/mattermost/mattermost/server/v8Go | >= 11.4.0-rc1, < 11.4.1 | 11.4.1 |
github.com/mattermost/mattermost/server/v8Go | >= 11.3.0-rc1, < 11.3.2 | 11.3.2 |
github.com/mattermost/mattermost/server/v8Go | >= 11.2.0-rc1, < 11.2.3 | 11.2.3 |
github.com/mattermost/mattermost/server/v8Go | >= 10.11.0-rc1, < 10.11.11 | 10.11.11 |
github.com/mattermost/mattermost/server/v8Go | >= 8.0.0-20260105080200-d27a2195068d, < 8.0.0-20260217110922-b7d4a1f1f59b | 8.0.0-20260217110922-b7d4a1f1f59b |
Affected products
1- Range: 11.2.0
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
3- github.com/advisories/GHSA-g7fp-cqj5-x8hfghsaADVISORY
- mattermost.com/security-updatesghsavendor-advisoryWEB
- nvd.nist.gov/vuln/detail/CVE-2026-4274ghsaADVISORY
News mentions
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