# CVE-2026-124551: ClassroomIO through 1.0.0 Cross-Organization Course Disclosure via Clone Endpoint

Status: published. Published: 2026-11-08. Updated: 2026-11-12.

ClassroomIO through 1.0.0 contains an authorization bypass vulnerability that allows authenticated users of any organization to clone other tenants' courses via the POST /course/:courseId/clone endpoint. Attackers who know a target course id can copy its sections, lessons, exercises, and quiz answer keys into their own organization, exposing private course content.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/classroomio/classroomio/commit/6630b73f8d53e316de6f575a170b093da6bf3cca

## Affected products and versions

- classroomio / classroomio (classroomio/classroomio): ≥ 0; ≤ 1.0.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N; source: CNA: VulnCheck

- CVSS 4.0: 6 (medium); CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/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; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.26% as of 2026-11-12; percentile 17.99%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-639

## Exploit evidence

- exploit: https://hackmd.io/@hieuPenguinnn/classroomio-course-clone-cross-org-content-exfiltration (ADP: CISA-ADP)

## References

- https://github.com/classroomio/classroomio/issues/1414 (CNA: VulnCheck; issue-tracking)

- https://github.com/classroomio/classroomio (CNA: VulnCheck; product)

- https://github.com/classroomio/classroomio/commit/6630b73f8d53e316de6f575a170b093da6bf3cca (CNA: VulnCheck; patch)

- https://hackmd.io/@hieuPenguinnn/classroomio-course-clone-cross-org-content-exfiltration (CNA: VulnCheck; technical-description)

- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/routes/course/course.ts#L584-L612 (CNA: VulnCheck; technical-description)

- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/services/course/clone.ts#L202-L290 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/classroomio-through-1.0.0-cross-organization-course-disclosure-via-clone-endpoint (CNA: VulnCheck; third-party-advisory)

- https://hackmd.io/@hieuPenguinnn/classroomio-course-clone-cross-org-content-exfiltration (ADP: CISA-ADP; exploit)

- https://github.com/classroomio/classroomio (disclosure@vulncheck.com)

- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/routes/course/course.ts#L584-L612 (disclosure@vulncheck.com)

- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/services/course/clone.ts#L202-L290 (disclosure@vulncheck.com)

- https://github.com/classroomio/classroomio/commit/6630b73f8d53e316de6f575a170b093da6bf3cca (disclosure@vulncheck.com)

- https://github.com/classroomio/classroomio/issues/1414 (disclosure@vulncheck.com)

- https://hackmd.io/@hieuPenguinnn/classroomio-course-clone-cross-org-content-exfiltration (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/classroomio-through-1.0.0-cross-organization-course-disclosure-via-clone-endpoint (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-124551; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-124551; retrieved 2026-11-08; source updated 2026-11-08

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-124551; retrieved 2026-11-12; source updated Not reported

Revision: 8830c6d7c0a4dfa3f574bec1972e3bc7e07868cec58e6864e0deb3fc52b474d7

Canonical: https://y2.dev/cve/CVE-2026-124551

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

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