---
title: "CVE-2026-55518: Avo: Missing Authorization in Avo Association Attach Endpoint Allows Unauthorized Relationship Manipulation and Privilege Escalation"
url: https://erroneo.us/security/cve/CVE-2026-55518/
description: "CVE-2026-55518 (avo (RubyGems)): 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…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-07-17
date_modified: 2026-07-20
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-55518"
kev: false
cvss: 9.6
epss: 0.00448
license: All rights reserved. Quote with attribution and a link.
---

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

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.4% , percentile 38: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 38% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes avo (RubyGems) <= 3.32.0, fixed in 3.32.1 ; avo (RubyGems) >= 4.0.0.beta.1, < 4.0.0.beta.51, fixed in 4.0.0.beta.51 . Check your lockfile, including transitive dependencies.

## What it is

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 ? 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.

## Affected packages

- RubyGems `avo` <= 3.32.0 → fixed: 3.32.1
- RubyGems `avo` >= 4.0.0.beta.1, < 4.0.0.beta.51 → fixed: 4.0.0.beta.51

## Affected products (CVE record)

- avo-hq avo: >= 4.0.0.beta.1, < 4.0.0.beta.51, < 3.32.1

## Severity

- GitHub_M CVSS 3.1: 9.6 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.6 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.45% probability of exploitation activity in the next 30 days; percentile 38.

## Sources

- [GitHub Advisory GHSA-8fq9-273g-6mrg](https://github.com/advisories/GHSA-8fq9-273g-6mrg)
- [CVE.org record CVE-2026-55518](https://www.cve.org/CVERecord?id=CVE-2026-55518)
- [NVD entry CVE-2026-55518](https://nvd.nist.gov/vuln/detail/CVE-2026-55518)
- [github.com](https://github.com/avo-hq/avo/security/advisories/GHSA-8fq9-273g-6mrg)
- [github.com](https://github.com/avo-hq/avo/pull/4568)
- [github.com](https://github.com/avo-hq/avo/commit/995928e586fd1788dd496bd51c4dbe4a79cb2b9c)
- [github.com](https://github.com/avo-hq/avo/releases/tag/v3.32.1)
- [github.com](https://github.com/rubysec/ruby-advisory-db/blob/master/gems/avo/CVE-2026-55518.yml)

---
Source page: https://erroneo.us/security/cve/CVE-2026-55518/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt