๐Ÿ›ก๏ธ CVE-2026-27656
๐ŸŸก CVSS 5.7 โ€” Medium โœ… No Known Exploit CWE-303 NVD
5.7
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590

Details

Severity Medium
CVSS Score 5.7
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:N
CWE CWE-303
Public Exploit โœ… No
Source NVD
Published 2026-03-25
Updated 2026-06-02
Modified 2026-03-31
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/mattermost/mattermost-server โ€” โ€”
github.com/mattermost/mattermost/server/v8 โ€” โ€”
mattermost-server 11.4.0 11.4.1

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