CVE-2026-9859

6.5 mediumEPSS 0.3%

Medium (6.5) in mattermost mattermost server. EPSS 0.3% chance of exploitation in the next 30 days.

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686

Severity

CVSS 3.1

6.5 medium

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS: 0.3% chance of exploitation in the next 30 days; higher than 27% of CVEs (scores of 2026-10-31)
CWE: CWE-863
Published: 2026-08-17
Modified: 2026-08-19
Record from: the NVD, synced 2026-10-19

Affected

mattermost:mattermost_server

References

https://mattermost.com/security-updates

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