CVE-2026-27656mediumCWE-303

CVE-2026-27656: fallo de gravedad media en Mattermost

Account Takeover via Substring Matching in OpenID Connect Authentication

Publicada el · Actualizada el

13Vexday Risk Score

Sin señal de explotación. Ningún artefacto público de explotación conocido hasta ahora.

ssvc Trackcvss 5.7epss 0.3%
probabilidad de explotación
0.3%top 78% de las CVE
explotación observada
noninguna fuente lo reporta
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:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:N
Productos afectados
Mattermost · Mattermost
CVEs relacionadas — Mattermost

En el mismo producto, de las más peligrosas a las menos.

CVE-2025-25279CRITICALArbitrary file read in Mattermost Boards via import & export board archiveEPSS 24.2%CVE-2021-37859HIGHReflected XSS in OAuth FlowEPSS 3.3%CVE-2022-3257LOWServer-side Denial of Service while processing a specifically crafted GIF fileEPSS 1.3%CVE-2022-4044MEDIUMAuthenticated user could send multiple requests containing a large Auto Responder Message payload and can crash a Mattermost serverEPSS 1.1%CVE-2022-3147LOWServer-side Denial of Service while processing a specifically crafted JPEG fileEPSS 1.0%CVE-2022-1982MEDIUMA crafted SVG attachment can crash a Mattermost serverEPSS 0.9%
Referencias
https://mattermost.com/security-updates