Compliance Impact

This vulnerability allows unauthenticated attackers to escalate privileges to super-admin level by exploiting improper validation of registration fields. Such unauthorized access to administrative functions can lead to unauthorized data access, modification, or deletion.

From a compliance perspective, this poses significant risks to standards like GDPR and HIPAA, which require strict access controls and protection of sensitive data. If exploited, the vulnerability could result in breaches of personal or protected health information, violating these regulations.

Therefore, organizations using affected versions of Grav CMS without the patch may fail to meet compliance requirements related to data confidentiality, integrity, and access control.

Useful 0 Not Useful 0

Executive Summary

CVE-2026-42613 is a critical vulnerability in the Grav CMS Login plugin before version 2.0.0-beta.2. The issue arises because the Login::register() method accepts attacker-controlled 'groups' and 'access' fields from the registration POST data without proper server-side validation.

When registration is enabled and these fields are included in the allowed fields list, an unauthenticated attacker can inject these fields during self-registration to gain super-admin privileges.

This happens because the validation method only checks common fields like username, password, and email, but ignores 'groups' and 'access', allowing malicious input to bypass security controls.

The vulnerability is fixed in version 2.0.0-beta.2 and later, where the registration handler explicitly strips privilege-related fields and logs warnings for injection attempts.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability allows an unauthenticated attacker to escalate their privileges by registering themselves with super-admin rights.

With super-admin access, the attacker can fully control the admin panel, potentially leading to remote code execution and complete compromise of the Grav CMS site.

The attack requires no privileges, no user interaction, and can be executed remotely over the network, making it highly severe.

Useful 0 Not Useful 0

Detection Guidance

This vulnerability can be detected by monitoring registration POST requests for the presence of privilege-related fields such as 'groups' or 'access' being submitted by unauthenticated users.

Specifically, look for registration attempts where the POST data includes parameters like groups[]=admins or access[admin][super]=true, which indicate attempts to inject admin privileges.

You can use network monitoring tools or web server logs to search for such suspicious registration requests.

• Use command-line tools like grep to scan web server access logs for POST requests containing 'groups' or 'access' fields, for example:
• grep -i 'groups' /var/log/apache2/access.log
• grep -i 'access' /var/log/apache2/access.log
• Use tools like tcpdump or Wireshark to capture and analyze HTTP POST traffic to the registration endpoint, filtering for these fields.

Useful 0 Not Useful 0

Mitigation Strategies

The immediate mitigation step is to upgrade the Grav Login plugin to version 3.8.2 or later, where the vulnerability is fixed by stripping client-supplied privilege fields from registration forms and logging injection attempts.

If upgrading immediately is not possible, ensure that the registration feature is disabled or that the 'groups' and 'access' fields are not included in the allowed fields list for user registration.

Additionally, review your configuration to prevent privilege-related fields from being accepted during registration.

Monitor logs for any suspicious registration attempts that include privilege escalation fields and respond accordingly.

Useful 0 Not Useful 0