Live › vulnerability › CVE-2026-63398
Coop, an open source moderation tool from ROOST, matches SAML logins by email alone without checking the organization. An attacker who administers one organization and holds a matching SAML signing key can sign in as a user in another organization.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-30 23:26 UTC. All times on this page are UTC.
Only Coop deployments that use SAML single sign-on, where more than one organization registers the same signing certificate. The attacker must administer one organization and control its signing key. Single-tenant installs or installs without SAML are not exposed.
No product ranges from the sources yet.
1.0.2.1.0.2 or later.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Coop is an open source review and moderation tool from ROOST. Prior to 1.0.2, the SAML strategy's verify callback resolved the authenticated user by email alone using kyselyUserFindByEmail, without binding the lookup to the organization in /saml/login/:orgId/callback. An attacker who administers an organization and controls its SAML IdP signing key can submit an assertion for a victim email to another organization's callback when that target organization has registered the same signing certificate. The assertion verifies against the target certificate, and the email resolves to the target user, creating a session as that user and allowing full cross-tenant account takeover without privileges in the target organization. Exploitation requires the unusual configuration in which the target certificate matches a signing key controlled by the attacker. This issue is fixed in version 1.0.2.
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