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.

Attack Vector Network

Attack Complexity Low

Privileges Required High

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
roostorg coop affected
Version Status Constraints
< 1.0.2 affected —

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Project Subscriptions

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Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/roostorg/coop/commit/d1be81b6b33abc1162ee6b9952d4bd1ca761b071 cve-icon cve-icon
https://github.com/roostorg/coop/pull/783 cve-icon cve-icon
https://github.com/roostorg/coop/releases/tag/1.0.2 cve-icon cve-icon
https://github.com/roostorg/coop/security/advisories/GHSA-2v93-383c-9fw2 cve-icon cve-icon
History

Fri, 30 Oct 2026 23:00:00 +0000

Type Values Removed Values Added
Description 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.
Title Coop has SAML cross-tenant authentication bypass
Weaknesses CWE-287
References
Metrics cvssV4_0

{'score': 7.4, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-30T22:44:43.092Z

Reserved: 2026-07-16T19:20:28.986Z

Link: CVE-2026-63398

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-30T23:17:14.850

Modified: 2026-10-30T23:17:14.850

Link: CVE-2026-63398

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-31T01:00:10Z

Weaknesses