PT-2026-28642 · Mattermost · Mattermost

Daw10

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CVE-2026-4274

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Published

2026-03-26

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Updated

2026-07-30

CVSS v3.1

5.4

Medium

VectorAV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Name of the Vulnerable Software and Affected Versions Mattermost versions 10.11.0 through 10.11.10 Mattermost versions 11.2.0 through 11.2.2 Mattermost versions 11.3.0 through 11.3.1 Mattermost versions 11.4.0
Description The software does not properly restrict team-level access when processing membership synchronization from a remote cluster. This allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel. This is achieved by sending crafted membership synchronization messages that trigger team membership assignment.
Recommendations Update Mattermost to a version later than 10.11.10. Update Mattermost to a version later than 11.2.2. Update Mattermost to a version later than 11.3.1. Update Mattermost to a version later than 11.4.0.

Exploit

Fix

DoS

Incorrect Authorization

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Weakness Enumeration

CWE-863

Related Identifiers

CVE-2026-4274
GHSA-G7FP-CQJ5-X8HF
GO-2026-5393
OPENSUSE-SU-2026:21483-1

Affected Products

Mattermost