CVE-2026-66399 in phpMyFAQ
Summary
by MITRE • 07/27/2026
phpMyFAQ before 4.1.6 contains a privilege escalation vulnerability in GroupController::updateMembers() that allows administrators with only group-management permissions to join privileged groups without verification of required rights. Attackers can add themselves to pre-existing groups holding user-management rights and immediately inherit those permissions to modify or delete user accounts.
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Analysis
by VulDB Data Team • 07/27/2026
This vulnerability exists within phpMyFAQ version 4.1.5 and earlier, specifically in the GroupController::updateMembers() method which handles group membership modifications. The flaw represents a classic privilege escalation issue where an attacker with limited group-management permissions can manipulate the system to gain elevated access rights. The vulnerability stems from insufficient authorization checks during the group membership update process, allowing unauthorized users to add themselves to groups that possess higher privileges without proper verification of their own entitlements.
The technical implementation of this weakness allows attackers to exploit a logic flaw in the permission validation mechanism. When administrators attempt to modify group memberships, the system fails to properly validate whether the requesting user has sufficient privileges to perform such operations on the target groups. This creates an opportunity for attackers to manipulate the group membership data structure directly through the updateMembers() function, effectively bypassing normal access control boundaries that should prevent users from gaining access to groups they are not authorized to join.
From an operational perspective, this vulnerability enables attackers to immediately inherit the full privileges of user-management groups without requiring additional authentication or approval processes. The impact is particularly severe because it allows adversaries to modify or delete user accounts, potentially compromising the entire user management system within the application. This privilege escalation can be executed silently without generating audit trails that would normally alert administrators to unauthorized access attempts, making detection more challenging.
The vulnerability aligns with CWE-285 which addresses improper authorization issues in software systems. It also maps to ATT&CK technique T1078 which covers valid accounts and privilege escalation through legitimate system access. The flaw demonstrates a failure in the principle of least privilege enforcement where users should only be able to perform actions that are explicitly granted to their current permission level. Organizations using affected versions of phpMyFAQ should immediately apply the patch available in version 4.1.6 which implements proper authorization checks before allowing group membership modifications.
Mitigation strategies include immediate deployment of the patched version 4.1.6 or higher, implementing additional monitoring of group membership changes, and establishing strict access controls for administrative functions. Security teams should also review existing user permissions to ensure that unnecessary group memberships are removed and implement regular audits of group assignments to identify any unauthorized changes that may have occurred. The vulnerability serves as a reminder of the critical importance of proper authorization validation in multi-tenant applications where role-based access control must be strictly enforced at every interaction point.