CVE-2026-30996: SAC-NFe Path Traversal Vulnerability

CVE-2026-30996 Overview

A directory traversal vulnerability has been discovered in SAC-NFe v2.0.02, a Brazilian electronic invoice management system. The vulnerability exists in the file handling logic of the download.php component, which fails to properly validate user-supplied input in GET request parameters. This security flaw allows unauthenticated remote attackers to traverse directories and read arbitrary files from the underlying system.

Critical Impact

Unauthenticated attackers can exploit this vulnerability remotely to access sensitive files including configuration files, application source code, and potentially credentials stored on the server.

Affected Products

• SAC-NFe v2.0.02
• Softsul SAC-NFe installations with vulnerable download.php component

Discovery Timeline

• 2026-04-15 - CVE-2026-30996 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2026-30996

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), commonly known as Path Traversal or Directory Traversal. The download.php component in SAC-NFe v2.0.02 accepts file path parameters through GET requests without adequate validation or sanitization. This allows attackers to manipulate the file path parameter using directory traversal sequences (such as ../) to escape the intended directory and access files anywhere on the file system that the web server process has read permissions for.

The attack can be executed remotely over the network without requiring authentication or user interaction, making it particularly dangerous for internet-facing installations. Successful exploitation results in unauthorized disclosure of confidential information, including system configuration files, application credentials, database connection strings, and potentially other sensitive data stored on the server.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the download.php file handling logic. The application fails to:

1. Properly sanitize user-supplied file path parameters
2. Implement path canonicalization to resolve symbolic links and relative paths
3. Restrict file access to the intended download directory
4. Validate that the resolved file path remains within the application's document root

The lack of these security controls allows directory traversal sequences to be processed, enabling attackers to navigate the file system hierarchy.

Attack Vector

The attack is executed via the network by sending a specially crafted HTTP GET request to the vulnerable download.php endpoint. Attackers can include directory traversal sequences (e.g., ../) in the file parameter to navigate outside the web application's intended directory structure. No authentication is required, and the attack can be performed without any user interaction, making it trivial to exploit.

For example, an attacker could craft a malicious request that traverses multiple parent directories to access system files like /etc/passwd or application configuration files containing database credentials. The vulnerability allows read access to any file readable by the web server process.

Detection Methods for CVE-2026-30996

Indicators of Compromise

• Web server access logs showing requests to download.php containing path traversal sequences (../, ..\, %2e%2e%2f, %2e%2e/)
• Unusual file access patterns in system audit logs targeting sensitive files outside the web root
• HTTP requests with encoded traversal sequences (URL encoding, double encoding, UTF-8 encoding)
• Failed file access attempts in application logs indicating traversal attempts outside permitted directories

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block requests containing directory traversal patterns
• Monitor web server logs for GET requests to download.php with suspicious path patterns
• Deploy intrusion detection/prevention systems (IDS/IPS) with signatures for path traversal attacks
• Enable file integrity monitoring on sensitive system files to detect unauthorized access

Monitoring Recommendations

• Configure real-time alerting for any access to download.php containing .. sequences or encoded variants
• Monitor access to sensitive files such as /etc/passwd, /etc/shadow, and application configuration files
• Implement audit logging on the web server to capture all file access operations
• Review web application logs periodically for anomalous request patterns targeting file download functionality

How to Mitigate CVE-2026-30996

Immediate Actions Required

• Restrict access to the vulnerable download.php component via firewall rules or web server configuration
• Implement input validation to reject any requests containing directory traversal sequences
• Apply the principle of least privilege to the web server process to minimize potential data exposure
• If possible, temporarily disable the vulnerable file download functionality until a patch is available

Patch Information

No official vendor patch information is available at this time. System administrators should monitor the CVE-2026-30996 Details page and Softsul Path Traversal Vulnerability documentation for updates from the vendor regarding security patches.

Workarounds

• Implement server-side input validation to sanitize file path parameters, stripping or rejecting traversal sequences
• Use a whitelist approach, only allowing downloads of specific predefined files rather than accepting arbitrary paths
• Deploy a Web Application Firewall (WAF) with rules to block path traversal patterns in requests
• Restrict the download.php endpoint to authenticated users only and implement access controls
• Run the web server process with minimal filesystem permissions to limit exposure of sensitive files

# Apache configuration to block directory traversal attempts
<LocationMatch "/download\.php">
    # Block requests containing path traversal sequences
    RewriteEngine On
    RewriteCond %{QUERY_STRING} (\.\./) [NC,OR]
    RewriteCond %{QUERY_STRING} (\.\.\\) [NC,OR]
    RewriteCond %{QUERY_STRING} (%2e%2e%2f) [NC,OR]
    RewriteCond %{QUERY_STRING} (%2e%2e/) [NC]
    RewriteRule .* - [F,L]
</LocationMatch>