CVE-2026-26746: Open Source Point Of Sale RCE Vulnerability

CVE-2026-26746 Overview

CVE-2026-26746 is a Local File Inclusion (LFI) vulnerability affecting OpenSourcePOS version 3.4.1. The vulnerability exists within the Sales.php::getInvoice() function, where improper input validation allows an attacker to manipulate the Invoice Type configuration parameter to read arbitrary files from the web server. This vulnerability is particularly dangerous as it can be chained with the application's file upload functionality to achieve Remote Code Execution (RCE), significantly escalating the potential impact.

Critical Impact

Attackers with low privileges can exploit this vulnerability to read sensitive server files and potentially achieve full remote code execution by chaining with file upload functionality.

Affected Products

• OpenSourcePOS Open Source Point of Sale version 3.4.1

Discovery Timeline

• 2026-02-20 - CVE-2026-26746 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2026-26746

Vulnerability Analysis

The vulnerability resides in the invoice generation functionality of OpenSourcePOS, specifically within the Sales.php controller's getInvoice() function. This function processes user-controlled input for the Invoice Type parameter without proper sanitization or path validation. When an authenticated user with low privileges submits a request to generate an invoice, they can manipulate the Invoice Type value to include path traversal sequences or absolute file paths.

The CWE-434 (Unrestricted Upload of File with Dangerous Type) classification indicates that the vulnerability chain involves improper file handling mechanisms. The LFI vulnerability alone allows attackers to read sensitive configuration files, application source code, and system files such as /etc/passwd. However, the true severity emerges when this vulnerability is combined with the file upload feature, enabling attackers to upload a malicious PHP file and then include it via the LFI to achieve code execution.

The attack requires network access and low-level authentication (such as a regular user account), but no user interaction is needed once the attacker has valid credentials. The scope of compromise extends to full system confidentiality, integrity, and availability loss.

Root Cause

The root cause of this vulnerability is insufficient input validation and path normalization in the getInvoice() function within Sales.php. The function accepts the Invoice Type configuration value and uses it directly in a file inclusion operation without verifying that the path resolves to an expected directory or file type. This allows directory traversal sequences (such as ../) to break out of the intended directory and access arbitrary files on the filesystem that the web server process has permissions to read.

Attack Vector

The attack vector is network-based, requiring an authenticated attacker to have access to the OpenSourcePOS web interface. The exploitation process involves sending a crafted HTTP request to the invoice generation endpoint with a manipulated Invoice Type parameter containing path traversal sequences. For the full RCE chain, an attacker would first upload a malicious PHP file through the application's file upload functionality, then use the LFI vulnerability to include and execute that file.

The attack flow involves:

1. Authenticating to the OpenSourcePOS application with a low-privileged account
2. Uploading a malicious PHP file through the file upload feature
3. Crafting a request to the getInvoice() endpoint with a manipulated Invoice Type parameter pointing to the uploaded malicious file
4. The server includes and executes the malicious PHP code, granting the attacker remote code execution

For detailed technical information, refer to the GitHub CVE-2026-26746 Documentation.

Detection Methods for CVE-2026-26746

Indicators of Compromise

• HTTP requests to invoice generation endpoints containing path traversal sequences such as ../ or ..%2f
• Unusual file access patterns in web server logs, particularly requests attempting to access files outside the application directory
• Evidence of suspicious file uploads with PHP or executable extensions
• Web server error logs showing attempts to include non-existent or restricted files

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in request parameters
• Monitor web server access logs for requests containing directory traversal sequences targeting the invoice or sales-related endpoints
• Deploy file integrity monitoring on the OpenSourcePOS upload directories to detect unauthorized file additions
• Configure intrusion detection systems to alert on requests with encoded traversal sequences (%2e%2e%2f, %252e, etc.)

Monitoring Recommendations

• Enable verbose logging on the OpenSourcePOS application to capture all file access operations
• Set up real-time alerting for any attempts to access system files like /etc/passwd or application configuration files
• Monitor for unusual process spawning from the web server process that could indicate successful code execution
• Regularly audit file upload directories for unexpected or suspicious files

How to Mitigate CVE-2026-26746

Immediate Actions Required

• Restrict access to the OpenSourcePOS application to trusted networks and users only until a patch is applied
• Review and remove any suspicious files from upload directories
• Implement input validation at the web server or WAF level to block path traversal attempts
• Audit user accounts and remove unnecessary access privileges
• Consider temporarily disabling the file upload functionality if not critical to operations

Patch Information

As of the last update on 2026-02-24, organizations should monitor the OpenSourcePOS GitHub Repository for security patches addressing this vulnerability. Review the CVE-2026-26746 security documentation for the latest remediation guidance.

Workarounds

• Implement strict input validation on the Invoice Type parameter to allow only alphanumeric characters and reject any path-related characters
• Configure web server restrictions to prevent the web process from reading files outside the application directory
• Use a web application firewall to filter requests containing path traversal patterns
• Restrict file upload functionality to specific file types and implement content-type verification

# Example Apache configuration to restrict file access
<Directory "/var/www/opensourcepos">
    # Deny access to sensitive files
    <FilesMatch "\.(php|ini|conf|log)$">
        Require all denied
    </FilesMatch>
    
    # Block path traversal attempts at the server level
    RewriteEngine On
    RewriteCond %{QUERY_STRING} (\.\./) [NC,OR]
    RewriteCond %{QUERY_STRING} (%2e%2e%2f) [NC]
    RewriteRule .* - [F,L]
</Directory>