Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
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| Mattermost | Mattermost | unaffected |
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Configuration 1 [-]
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No data.
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| Mattermost | Mattermost |
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Vendor Solution
Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14, 11.4.4 or higher.
| Source | ID | Title |
|---|---|---|
Github GHSA |
GHSA-8h9w-w78c-vvr3 | Mattermost does not verify remote cluster channel access when processing shared channel membership removals |
No CVSS v4.0
No CVSS v3.0
No CVSS v2
This CVE is not in the KEV list.
Exploit prediction score: < 1% (0.152% probability within 30 days)
| Link | Providers |
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| https://mattermost.com/security-updates |
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| First Time appeared |
Mattermost mattermost Server
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| CPEs | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Mattermost mattermost Server
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| Metrics |
ssvc
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| First Time appeared |
Mattermost
Mattermost mattermost |
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| Vendors & Products |
Mattermost
Mattermost mattermost |
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| Description | Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access. Mattermost Advisory ID: MMSA-2026-00576 | |
| Title | Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels | |
| Weaknesses | CWE-863 | |
| References |
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| Metrics |
cvssV3_1
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