Live › vulnerability › CVE-2026-19076
Go to dashboardMattermost fails to reject OAuth application sessions at its account type switch endpoint, POST /api/v4/users/login/switch. An attacker holding a valid OAuth bearer token for a user can set a password on that SSO-backed account and detach it from the identity provider, which gives them permanent control of the account.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.
Self-hosted or managed Mattermost servers in the listed version ranges that use SSO (such as SAML, GitLab or OAuth identity providers) with OAuth applications enabled. Exposure requires a valid OAuth bearer token for the target user, so teams without OAuth apps issuing tokens face less risk.
No product ranges from the sources yet.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to reject OAuth application sessions in the account type switch endpoint, which allows an attacker with a valid OAuth bearer token for a target user to permanently take over that user's SSO-backed account by setting an attacker-controlled password and detaching the account from its identity provider via a crafted request to POST /api/v4/users/login/switch.. Mattermost Advisory ID: MMSA-2026-00758
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