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

Advisory record · `GHSA-8fq9-273g-6mrg`

- **Identifiers:** `GHSA-8fq9-273g-6mrg` · `CVE-2026-55518`
- **State:** Confirmed
- **Severity:** CVSS 9.6 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-639](https://cwe.mitre.org/data/definitions/639.html) · [CWE-862](https://cwe.mitre.org/data/definitions/862.html) · [CWE-863](https://cwe.mitre.org/data/definitions/863.html)
- **Tags:** [Broken access control](https://agentprime.io/advisories/tag/access-control.md)
- **Published:** 17 Jun 2026
- **Updated:** 18 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Jun 2026, 18:49 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.6: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `avo` (RubyGems): affected `<3.32.1 || >=4.0.0.beta.1, <4.0.0.beta.51`; fixed in `3.32.1`, `4.0.0.beta.51`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.6 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0041, the 35th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 17 Jun 2026. New records show when each source confirmed them.

## Sources

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

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-8fq9-273g-6mrg>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-8fq9-273g-6mrg/>. Everything for agents: <https://agentprime.io/llms.txt>.