CVE-2026-63398

7.4 HIGH 0.2% exploit odds Fix listed Auth & access

What it is

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.

At a glance

Exploitability: Can be exploited over the network with an admin-level account. High risk of data exposure, data tampering.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-16 19:20 UTC ReservedThe CVE id was reserved by its CNA
2026-10-30 23:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-11-02 19:35 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 7.4 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-10-30 23:17 UTC
Last modified: 2026-11-02 19:35 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-287 · Improper authentication
Record status: Deferred

Attack profile CVSS 4.0 · 7.4

Attack vector: Network
Complexity: Low
Attack requirements: Present
Privileges needed: High
User interaction: None
Confidentiality: High
Integrity: High
Availability: None

Raw 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-63398.md and follow it. Check whether this project is affected by CVE-2026-63398. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record