# CVE-2026-42205: Avo broken access control in ActionsController

Source: https://junglewise.ai/threats/cve-2026-42205-avo-broken-access-control-in-actionscontroller  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-08. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-42205 · Severity: high · CVSS 8.8 · Published 2026-05-08

Avo is a framework used to build administration panels for Ruby on Rails applications. A security flaw allows logged-in users to bypass intended restrictions and execute administrative actions they are not authorized to perform. This could lead to unauthorized data changes, such as a regular user granting themselves administrator privileges or deleting sensitive records.

Technologies: [avo (RubyGems)](https://junglewise.ai/threats/technologies/avo). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-42205 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42205 being exploited in the wild.

**How severe is CVE-2026-42205?** High severity, with a CVSS score of 8.8, published 8 May 2026.

**Which products and versions are affected?** avo (RubyGems) < 3.31.2, ECOSYSTEM:introduced=0,fixed=3.31.2.

**Is there a fix for CVE-2026-42205?** Yes. avo (RubyGems): upgrade to 3.31.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-42205 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42205?** Check whether you run avo (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- avo (RubyGems): upgrade to 3.31.2 or later

  ```sh
  bundle update avo
  ```


## Technical details

A broken access control vulnerability exists in the `ActionsController` of the Avo framework (v3.x) due to insecure action lookup logic in the `action_class` method. The controller identifies the action class to execute by searching through all descendants of `Avo::BaseAction` based on a user-provided `action_id` parameter, without verifying if that action is registered for the specific resource context in the request URL. An authenticated attacker can exploit this by sending a POST request to a legitimate resource endpoint (e.g., posts) while specifying a sensitive action ID (e.g., ToggleAdmin) and a target record ID. This allows for privilege escalation and unauthorized data manipulation across the application. The issue is fixed in version 3.31.2.

## Affected products

- avo-hq avo < 3.31.2

## Identifiers

- CVE-2026-42205
- GHSA-qc5p-3mg5-9fh8

## Timeline

- 2026-04-20: disclosed: Advisory published by vendor
- 2026-04-24: advisory: GitHub Advisory published
- 2026-05-08: other: NVD published date

## References

- [https://api.github.com/users/xIllunight](https://api.github.com/users/xIllunight)
- [https://github.com/xIllunight](https://github.com/xIllunight)
- [https://api.github.com/users/xIllunight/gists%7B/gist_id%7D](https://api.github.com/users/xIllunight/gists%7B/gist_id%7D)
- [https://api.github.com/users/xIllunight/repos](https://api.github.com/users/xIllunight/repos)
- [https://avatars.githubusercontent.com/u/271749162?v=4](https://avatars.githubusercontent.com/u/271749162?v=4)
- [https://api.github.com/users/xIllunight/events%7B/privacy%7D](https://api.github.com/users/xIllunight/events%7B/privacy%7D)

## Related threats

- [Avo missing upload authorization in AttachmentsController](https://junglewise.ai/threats/cve-2026-53769-avo-missing-upload-authorization-in-attachmentscontroller)
- [Avo missing authorization in association attach endpoint](https://junglewise.ai/threats/cve-2026-55518-avo-missing-authorization-in-association-attach-endpoint)
- [Avo has a XSS vulnerability on `return_to` param](https://junglewise.ai/threats/cve-2026-33209-avo-has-a-xss-vulnerability-on-return-to-param)
- [Cross-site scripting (XSS) in Action messages on Avo](https://junglewise.ai/threats/cve-2024-22411-cross-site-scripting-xss-in-action-messages-on-avo)
- [avo vulnerable to stored cross-site scripting (XSS) in key_value field](https://junglewise.ai/threats/cve-2024-22191-avo-vulnerable-to-stored-cross-site-scripting-xss-in-key-value)