CVE-2026-4191: node-api-postgres Auth Bypass Vulnerability

CVE-2026-4191 Overview

A critical unrestricted file upload vulnerability has been discovered in JawherKl node-api-postgres up to version 2.5. The vulnerability affects the path.extname function within the index.js file of the Profile Picture Handler component, allowing attackers to upload arbitrary files without proper validation. This security flaw can be exploited remotely, potentially leading to remote code execution, data compromise, or further system infiltration.

Critical Impact

This unrestricted file upload vulnerability in the Profile Picture Handler allows remote attackers to bypass file type restrictions and upload malicious files, potentially achieving arbitrary code execution on the target server.

Affected Products

• JawherKl node-api-postgres up to version 2.5
• Applications using the Profile Picture Handler component in index.js
• Systems exposing the affected file upload functionality to untrusted networks

Discovery Timeline

• 2026-03-16 - CVE-2026-4191 published to NVD
• 2026-03-16 - Last updated in NVD database

Technical Details for CVE-2026-4191

Vulnerability Analysis

The vulnerability resides in the Profile Picture Handler component of node-api-postgres, specifically within the path.extname function implementation in index.js. The flaw stems from improper access control (CWE-284) during file upload operations, where the application fails to adequately validate or restrict the types of files that can be uploaded through the profile picture functionality.

When processing file uploads, the vulnerable code does not properly sanitize or verify the file extension and content type, allowing attackers to upload files with arbitrary extensions. This includes potentially dangerous file types such as executable scripts, web shells, or other malicious payloads that could be executed by the server.

The network-accessible nature of this vulnerability means that any attacker with network access to the affected application can exploit this flaw without requiring authentication or user interaction. An exploit has been publicly disclosed, increasing the immediate risk to unpatched systems.

Root Cause

The root cause of this vulnerability is improper access control and insufficient input validation in the file upload mechanism. The path.extname function is used to extract file extensions, but the application does not implement adequate safeguards to:

1. Validate file extensions against an allowlist of permitted types
2. Verify that the actual file content matches the declared file type
3. Prevent double-extension attacks or null byte injection
4. Restrict the storage location of uploaded files

This allows attackers to bypass intended file type restrictions and upload arbitrary content to the server.

Attack Vector

The attack is carried out remotely over the network by exploiting the profile picture upload functionality. An attacker can craft a malicious HTTP request containing a file with a dangerous extension or misleading content type. The vulnerable path.extname function fails to properly validate the upload, allowing the malicious file to be stored on the server.

Once uploaded, depending on the server configuration and file storage location, the attacker may be able to:

• Execute uploaded scripts directly through web access
• Overwrite critical application files
• Store malware for later retrieval
• Establish persistent backdoor access

Technical details and proof-of-concept information are available through the HackMD Security Documentation and VulDB #351098.

Detection Methods for CVE-2026-4191

Indicators of Compromise

• Unusual file types appearing in profile picture storage directories (e.g., .php, .jsp, .exe, .sh)
• Web server logs showing POST requests to profile upload endpoints with suspicious file extensions
• Unexpected executable files or scripts in user upload directories
• Anomalous outbound network connections originating from the web server process

Detection Strategies

• Implement file integrity monitoring on upload directories to detect unauthorized file additions
• Configure web application firewall (WAF) rules to inspect file upload requests for suspicious content
• Enable detailed logging for all file upload operations including file names, extensions, and source IPs
• Deploy endpoint detection solutions to monitor for web shell activity or malicious script execution

Monitoring Recommendations

• Monitor upload directory file system events for creation of files with executable extensions
• Set up alerts for HTTP requests to upload endpoints containing unusual MIME types or extensions
• Review web server access logs regularly for attempts to access non-image files in profile picture directories
• Implement network traffic analysis to detect command-and-control communications from compromised servers

How to Mitigate CVE-2026-4191

Immediate Actions Required

• Upgrade JawherKl node-api-postgres beyond version 2.5 when a patch becomes available
• Implement server-side file type validation using allowlists for permitted extensions (e.g., .jpg, .png, .gif)
• Add content-type verification to ensure uploaded files match their declared MIME types
• Store uploaded files outside the web root directory to prevent direct execution
• Restrict file permissions on upload directories to prevent script execution

Patch Information

As of the last update, the vendor (JawherKl) was contacted about this vulnerability but did not respond. Organizations using node-api-postgres should monitor for security updates and consider implementing the workarounds below until an official patch is released. Additional vulnerability details can be found through VulDB CTI ID #351098.

Workarounds

• Implement a strict file extension allowlist in the application layer, permitting only image formats
• Use server-side content inspection to validate file headers match expected image formats
• Rename uploaded files to random identifiers and store original names in a database
• Configure the web server to disable script execution in upload directories
• Deploy a web application firewall with rules to block suspicious file upload attempts

# Configuration example - Disable script execution in upload directories (Apache)
# Add to .htaccess in the uploads directory
<Directory /var/www/app/uploads>
    Options -ExecCGI -Indexes
    RemoveHandler .php .phtml .php3 .php4 .php5 .phps
    AddType text/plain .php .phtml .php3 .php4 .php5 .phps
    php_flag engine off
</Directory>