CVE-2026-33730: Open Source Point Of Sale Auth Bypass

CVE-2026-33730 Overview

Open Source Point of Sale (opensourcepos) is a web-based point of sale application written in PHP using the CodeIgniter framework. CVE-2026-33730 is an Insecure Direct Object Reference (IDOR) vulnerability that allows an authenticated low-privileged user to access the password change functionality of other users, including administrators, by manipulating the employee_id parameter. The application fails to verify object ownership or enforce proper authorization checks, enabling horizontal and vertical privilege escalation through unauthorized password modifications.

Critical Impact

Authenticated attackers can compromise administrator accounts by changing their passwords, leading to complete system takeover of the point of sale application and potential access to sensitive financial and customer data.

Affected Products

• Open Source Point of Sale (opensourcepos) versions prior to 3.4.2
• opensourcepos open_source_point_of_sale

Discovery Timeline

• 2026-03-27 - CVE-2026-33730 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-33730

Vulnerability Analysis

This vulnerability represents a classic Insecure Direct Object Reference (IDOR) flaw classified under CWE-639 (Authorization Bypass Through User-Controlled Key). The vulnerable getChangePassword() function in app/Controllers/Home.php accepts an employee_id parameter that determines which user's password can be modified. The original implementation used the can_modify_employee() method for authorization checks, but this method failed to properly restrict access based on the authenticated user's actual permissions.

An authenticated low-privileged user could simply enumerate or guess valid employee_id values and submit password change requests for arbitrary accounts. Since point of sale systems typically contain sensitive financial transaction data, customer information, and business records, the ability to compromise administrator accounts poses significant operational and compliance risks.

Root Cause

The root cause lies in insufficient object-level authorization within the password change functionality. The original can_modify_employee() check did not adequately verify that the current user has legitimate ownership or administrative rights over the targeted employee_id. The application trusted user-supplied input to determine which account's password should be modified without proper server-side validation of access rights.

Attack Vector

The attack vector is network-based and requires low-privileged authentication. An attacker with any valid user account can exploit this vulnerability through the following process:

1. Authenticate to the opensourcepos application with a low-privileged account
2. Navigate to the password change functionality
3. Intercept and modify the HTTP request, changing the employee_id parameter to target a different user (such as an administrator)
4. Submit the modified request to change the victim's password to an attacker-controlled value
5. Log in as the compromised user with the newly set password

The vulnerability can be exploited via simple parameter manipulation in HTTP requests, requiring no specialized tools beyond a web browser or proxy interceptor.

     /**
      * Load "change employee password" form
      *
-     * @return string
+     * @return ResponseInterface|string
      * @noinspection PhpUnused
      */
-    public function getChangePassword(int $employeeId = NEW_ENTRY): string
+    public function getChangePassword(int $employeeId = NEW_ENTRY)
     {
         $loggedInEmployee = $this->employee->get_logged_in_employee_info();
         $currentPersonId = $loggedInEmployee->person_id;

         $employeeId = $employeeId === NEW_ENTRY ? $currentPersonId : $employeeId;

-        if (!$this->employee->can_modify_employee($employeeId, $currentPersonId)) {
-            header('Location: ' . base_url('no_access/home/home'));
-            exit();
+        if (!$this->employee->isAdmin($currentPersonId) && $employeeId !== $currentPersonId) {
+            return $this->response->setStatusCode(403)->setBody(lang('Employees.unauthorized_modify'));
         }

         $person_info = $this->employee->get_info($employeeId);

Source: GitHub Commit ee4d44ed396097d6010c5490ab4fd7cfae694624

The patch introduces proper object-level authorization by explicitly checking if the current user is an administrator OR if they are attempting to modify their own account. Non-admin users can now only change their own password, while admin users retain the ability to modify any account. The fix also improves error handling by returning a proper HTTP 403 status code instead of a redirect.

Detection Methods for CVE-2026-33730

Indicators of Compromise

• Unusual password change requests where the employee_id parameter differs from the authenticated user's ID
• Multiple password change attempts targeting different employee accounts from a single session
• Successful password changes for administrator accounts initiated by non-admin user sessions
• HTTP requests to password change endpoints with sequentially enumerated employee_id values

Detection Strategies

• Implement web application firewall rules to alert on password change requests where the target user differs from the authenticated session
• Review application logs for patterns of parameter manipulation in sensitive functionality endpoints
• Monitor authentication logs for sudden administrator password changes followed by login activity from new IP addresses
• Enable detailed logging on the password change functionality to capture the relationship between requester and target accounts

Monitoring Recommendations

• Configure alerts for any password modification activity involving administrator-level accounts
• Implement anomaly detection for bulk parameter enumeration patterns in HTTP request logs
• Monitor for failed authorization attempts (HTTP 403 responses) to password change endpoints as indicators of exploitation attempts
• Establish baseline patterns for legitimate password change behavior and alert on deviations

How to Mitigate CVE-2026-33730

Immediate Actions Required

• Upgrade opensourcepos to version 3.4.2 or later immediately to apply the security patch
• Audit password change logs to identify any unauthorized modifications that may have occurred
• Force password resets for all administrator accounts as a precautionary measure
• Review all user accounts for suspicious activity or unauthorized privilege changes

Patch Information

The vulnerability is addressed in opensourcepos version 3.4.2. The fix implements object-level authorization checks that verify the current user is either an administrator or is modifying their own account. The patch can be reviewed in commit ee4d44ed396097d6010c5490ab4fd7cfae694624. For detailed information, refer to the GitHub Security Advisory GHSA-mcc2-8rp2-q6ch.

Workarounds

• If immediate patching is not possible, restrict network access to the opensourcepos application to trusted IP ranges only
• Implement additional authentication factors for administrator accounts to reduce the impact of password compromise
• Deploy a web application firewall rule to block or alert on password change requests where employee_id parameter manipulation is detected
• Temporarily disable or restrict the password change functionality until the patch can be applied

# Configuration example - Restrict access to opensourcepos at the web server level
# Apache configuration to limit access to trusted networks
<Location "/home/changePassword">
    Require ip 192.168.1.0/24
    Require ip 10.0.0.0/8
</Location>