Avo Framework Broken Access Control Vulnerability

A critical broken access control vulnerability exists within the Avo framework, specifically affecting version 3.x. This vulnerability resides in the ActionsController and stems from an insecure action lookup mechanism. An authenticated user, regardless of their privilege level, can execute any Action class (descendants of Avo::BaseAction) on any resource within the application. This occurs because the system fails to validate whether the requested action is legitimately registered or permitted for the resource context specified in the request. The absence of this verification allows for the circumvention of intended resource-action mappings. Successful exploitation leads to privilege escalation, unauthorized data manipulation, and potential compromise of the application’s integrity. It is recommended to upgrade to version 3.31.2 or later, which addresses this vulnerability.

Attack Chain

1. An attacker authenticates to the Avo admin panel with low-level privileges.
2. The attacker identifies a sensitive action class, such as Avo::Actions::ToggleAdmin.
3. The attacker identifies a target record ID, such as a user ID they wish to manipulate.
4. The attacker crafts a POST request to a resource endpoint where the target action is NOT registered (e.g., /admin/resources/posts/actions).
5. The POST request includes a payload containing the action_id parameter set to the sensitive action class (Avo::Actions::ToggleAdmin).
6. The POST request also includes a fields[avo_resource_ids] parameter set to the target record ID.
7. Due to the insecure action lookup in Avo::ActionsController, the server executes the ToggleAdmin action on the specified user ID.
8. The attacker’s privileges are escalated, or unauthorized data manipulation occurs due to the successful execution of the unintended action.

Impact

The exploitation of this broken access control vulnerability can have severe consequences. A successful attack can lead to privilege escalation, allowing attackers to gain administrative control over the application. Unauthorized operations can be performed, leading to data breaches or data manipulation. Sensitive actions designed for restricted resources can be triggered against any record ID, potentially compromising the integrity and confidentiality of data. The impact includes unauthorized deletion, archival, or updates to records, causing reputational damage and potential financial losses.

Recommendation

• Upgrade to Avo version 3.31.2 or later, which contains the necessary fix to restrict action lookup to registered actions for the current resource context.
• Deploy the Sigma rule Detect Avo Unauthorized Action Execution to monitor for attempts to execute actions on resources where they are not registered.
• Review and audit existing Avo action registrations to ensure that actions are appropriately mapped to resources within the application.