CVE-2026-10103

4.3 mediumEPSS 0.2%

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing arbitrary post IDs in channels shared with that remote.. Mattermost Advisory ID: MMSA-2026-00689

Severity

CVSS 3.1

4.3 medium

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

EPSS: 0.2% chance of exploitation in the next 30 days; higher than 15% of CVEs (scores of 2026-10-31)
CWE: CWE-639
Published: 2026-07-13
Modified: 2026-07-14
Record from: the NVD, synced 2026-10-19

Affected

mattermost:mattermost_server

References

https://mattermost.com/security-updates

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