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Response snapshot Oct 31, 2026, 01:26 UTC

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VulnerabilityCVE-2026-63398

Coop is an open source review and moderation tool from ROOST.

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.

At a glance

Exploited
Not known
Severity
7.4 High (CVSS 4.0)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-63398 (opens a new tab)

What happened

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.

Scores and how they were measured

CVSS base severity

7.4

Version 4.0As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-63398 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). Coop is an open source review and moderation tool from ROOST. (CVE-2026-63398). https://kevwire.com/record/CVE-2026-63398

MLA

"Coop is an open source review and moderation tool from ROOST. (CVE-2026-63398)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-63398.

Chicago

KEVWire. "Coop is an open source review and moderation tool from ROOST. (CVE-2026-63398)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-63398.

Evidence summary (plain text)

Coop is an open source review and moderation tool from ROOST. (Oct 30, 2026).
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.
CVSS 7.4 (version 4.0; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-63398).
Sources:
NVD CVE-2026-63398: https://nvd.nist.gov/vuln/detail/CVE-2026-63398
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T23:16:04.425Z&lastModEndDate=2026-10-31T00:50:55.911Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T22:40:58.681Z&lastModEndDate=2026-10-31T00:15:58.432Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T22:05:59.313Z&lastModEndDate=2026-10-30T23:40:58.124Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-63398.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 31, 2026, 00:50 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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