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52 changes: 52 additions & 0 deletions gems/avo/CVE-2026-55518.yml
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---
gem: avo
cve: 2026-55518
ghsa: 8fq9-273g-6mrg
url: https://www.cve.org/CVERecord?id=CVE-2026-55518
title: Avo - Missing Authorization in Avo Association Attach Endpoint
Allows Unauthorized Relationship Manipulation and Privilege Escalation
date: 2026-06-17
description: |
## Summary

A critical missing authorization flaw exists in Avo's association attach
workflow. The UI and `GET /resources/:resource/:id/:related/new` path
can check `attach_<association>?`, but the actual write endpoint,
`POST /resources/:resource/:id/:related`, does not run the same
authorization check before mutating the association.

As a result, an authenticated low-privileged Avo user can bypass
hidden/disabled attach controls and directly attach related records
to a parent record by sending a crafted POST request. In applications
where associations represent teams, tenants, roles, projects, users,
memberships, ownership, or other authorization-bearing relationships,
this can lead to privilege escalation and cross-tenant data exposure.

## Impact

This vulnerability allows unauthorized relationship manipulation
through Avo.

Depending on the affected association, the impact can include:

- Privilege escalation by attaching a user to an admin group,
privileged project, tenant, organization, role, or membership record.
- Cross-tenant data exposure when tenant/user/project membership
determines record visibility.
- Integrity loss by changing ownership, assignment, access-control
relationships, or business workflow state.
- Policy bypass even when Avo UI controls correctly hide the attach
button or deny the attach form.
cvss_v3: 9.6
patched_versions:
- "~> 3.32.1"
- ">= 4.0.0.beta.51"
related:
url:
- https://www.cve.org/CVERecord?id=CVE-2026-55518
- https://advisories.gitlab.com/gem/avo/CVE-2026-55518
- https://github.com/avo-hq/avo/security/advisories/GHSA-8fq9-273g-6mrg
- https://github.com/advisories/GHSA-8fq9-273g-6mrg
notes: |
- cvss_v3 from GHSA, no value for cvss_v2 or cvss_v4
- CVE is reserved, but not published