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CVSS v3.1
5.7
EPSS
0.18%
Published
Mar 25, 2026
Modified
Mar 26, 2026
Public PoC / Exploit (1)
All weaponized →Links to public security research (Exploit-DB, Nuclei, Trickest, GitHub) for defensive use only.
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
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:NWeaknesses (CWE)
Affected Products (4)
References (1)