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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.6 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-55518: 0.41% estimated exploitation activity in the next 30 days; percentile 35.42 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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. Details The association attach route writes relationships through Avo::AssociationsController#create: The controller registers an attach authorization callback only for new, not for create: The new action is only the form-rendering step. The actual mutation…

Published by the source

17 Jun 2026, 18:49 UTC

Last modified by the source

18 Jul 2026, 17:22 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8fq9-273g-6mrg

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# Patch Next advisory brief: CVE-2026-55518

Advisory: Avo: Missing Authorization in Avo Association Attach Endpoint Allows Unauthorized Relationship Manipulation and Privilege Escalation
IDs: CVE-2026-55518, GHSA-8fq9-273g-6mrg
Record: https://patchnext.com/advisories/cve-2026-55518 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: avo 4.0.0.beta.51, 3.32.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems avo: affected <= 3.32.0; >= 4.0.0.beta.1, < 4.0.0.beta.51; fixed in 3.32.1, 4.0.0.beta.51

## Suggested inspection (read-only)
- RubyGems avo: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on avo.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-8fq9-273g-6mrg (GitHub-reviewed advisory GHSA-8fq9-273g-6mrg lists affected ranges: RubyGems avo >=0 =4.0.0.beta.1 <4.0.0.beta.51)

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