CVE-2026-10103

Authenticated remote cluster can modify or delete posts it does not own in Mattermost Connected Workspaces shared channels

State: Published
Severity: 4.3 Medium
Published: Jul 13, 2026
Updated: Jul 14, 2026
Reserved: May 29, 2026

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Description

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

Scores

CVSS	Score	Vector	Source
3.1	4.3 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N	Mattermost

Weaknesses

CWE-639 Authorization Bypass Through User-Controlled Key

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.2Affected 11.6.0 through 11.6.4Affected 10.11.0 through 10.11.19Affected 11.8.0Not affected 11.7.3Not affected 11.6.5Not affected 10.11.20Not affected

References

MMSA-2026-00689vendor-advisory

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