# CVE-2026-63398: Coop SAML cross-organization account takeover

Source: https://junglewise.ai/threats/cve-2026-63398-coop-is-an-open-source-review-and-moderation-tool-from-roost  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

CVE-2026-63398 · Severity: info · Published 2026-10-30

Coop is an open source review and moderation tool that uses SAML authentication to manage user access across multiple organizations. Attackers who control a SAML signing certificate and administer one organization can forge login assertions to impersonate users in other organizations that have registered the same certificate, achieving complete account takeover without needing legitimate access to the target organization.

Technologies: [ROOST Coop](https://junglewise.ai/threats/technologies/coop). Vendors: [ROOST](https://junglewise.ai/threats/vendors/roost).

## Quick answers

**Is CVE-2026-63398 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63398 being exploited in the wild.

**How severe is CVE-2026-63398?** Informational severity, published 30 October 2026.

**Which products and versions are affected?** ROOST Coop prior to 1.0.2.

**Is there a fix for CVE-2026-63398?** Yes: fixed in 1.0.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63398 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-63398?** Check whether you run ROOST Coop at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 1.0.2

## Technical details

The SAML verify callback resolved authenticated users by email alone using kyselyUserFindByEmail, without binding the lookup to the organization specified in the callback path (/saml/login/:orgId). Because email addresses can exist across multiple tenants, an attacker controlling an organization's IdP signing key could submit a SAML assertion for a victim's email to another organization's callback; if both organizations had registered the same signing certificate, the assertion would verify and resolve to the target user. The fix adds organization-scoped user lookup via kyselyUserFindByEmailAndOrg to bind resolution to the callback organization.

## Affected products

- ROOST Coop prior to 1.0.2

## Timeline

- 2026-10-30: disclosed
- 2026-06-16: patched

## References

- [https://github.com/roostorg/coop/commit/d1be81b6b33abc1162ee6b9952d4bd1ca761b071](https://github.com/roostorg/coop/commit/d1be81b6b33abc1162ee6b9952d4bd1ca761b071)
- [https://github.com/roostorg/coop/pull/783](https://github.com/roostorg/coop/pull/783)

## Related threats

- [ROOST Coop unauthorized cross-organization queue access](https://junglewise.ai/threats/cve-2026-63401-coop-is-an-open-source-review-and-moderation-tool-from-roost)
- [ROOST Coop session fixation on password reset](https://junglewise.ai/threats/cve-2026-63400-coop-is-an-open-source-review-and-moderation-tool-from-roost)
- [ROOST Coop unauthenticated GraphQL organization creation](https://junglewise.ai/threats/cve-2026-63399-coop-is-an-open-source-review-and-moderation-tool-from-roost)
- [ROOST Coop unauthenticated GraphQL data exposure](https://junglewise.ai/threats/cve-2026-63396-coop-is-an-open-source-review-and-moderation-tool-from-roost)