---
id: CVE-2026-63398
title: Coop has SAML cross-tenant authentication bypass
summary: >-
  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
  organizatio…
severity: high
cvss: 7.4
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-287
vendor: roostorg
product: coop
affected:
  - coop < 1.0.2
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-11-02T17:09:34.942380Z'
published: '2026-10-30'
updated: '2026-11-02'
sourceUpdated: '2026-11-02T17:56:56.369Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-63398'
references:
  - url: 'https://github.com/roostorg/coop/security/advisories/GHSA-2v93-383c-9fw2'
    label: 'https://github.com/roostorg/coop/security/advisories/GHSA-2v93-383c-9fw2'
  - url: 'https://github.com/roostorg/coop/pull/783'
    label: 'https://github.com/roostorg/coop/pull/783'
  - url: >-
      https://github.com/roostorg/coop/commit/d1be81b6b33abc1162ee6b9952d4bd1ca761b071
    label: >-
      https://github.com/roostorg/coop/commit/d1be81b6b33abc1162ee6b9952d4bd1ca761b071
  - url: 'https://github.com/roostorg/coop/releases/tag/1.0.2'
    label: 'https://github.com/roostorg/coop/releases/tag/1.0.2'
tags:
  - cve.org
epss: 0.00184
epssPercentile: 0.08076
ingestedAt: '2026-11-05T19:30:42.758Z'
---

## Overview

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.

## Affected

- `coop < 1.0.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.