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GO-2026-5256 Mattermost does not verify remote cluster channel access when processing shared channel membership removals in github.com/mattermost/mattermost-server

🗓️ 25 Jun 2026 18:43:15Reported by GoogleType 
osv
 osv🔗 osv.dev👁 2 Views

Mattermost server fails to verify remote cluster channel access during shared channel removals.

Related
Refs
ReporterTitlePublishedViews
Family
ATTACKERKB		CVE-2026-28759
18 May 202606:50
–attackerkb
Circl		CVE-2026-28759
18 May 202608:34
–circl
CNNVD		Mattermost 安全漏洞
18 May 202600:00
–cnnvd
CVE		CVE-2026-28759
18 May 202606:50
–cve
Cvelist		CVE-2026-28759 Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels
18 May 202606:50
–cvelist
EUVD		EUVD-2026-30738
18 May 202606:50
–euvd
Github Security Blog		Mattermost does not verify remote cluster channel access when processing shared channel membership removals
18 May 202609:31
–github
Tenable Nessus		Mattermost Server 10.11.x <= 10.11.13 / 11.4.x <= 11.4.3 / 11.5.x <= 11.5.1 Multiple Vulnerabilities (MMSA-2026-00573 / MMSA-2026-00576 / MMSA-2026-00591 / MMSA-2026-00605 / MMSA-2026-00607 / MMSA-2026-00608 / MMSA-2026-00614 / MMSA-2026-00627)
22 May 202600:00
–nessus
NVD		CVE-2026-28759
18 May 202608:16
–nvd
OSV		GHSA-8H9W-W78C-VVR3 Mattermost does not verify remote cluster channel access when processing shared channel membership removals
18 May 202609:31
–osv
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25 Jun 2026 19:45Current
5.9Medium risk
Vulners AI Score5.9
CVSS 3.14.3
EPSS0.00152
SSVC
Mattermost serverremote cluster accessshared channelmembership removalsvulnerability advisoryversions mapping
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