CVE-2026-5210: Leave Application System Path Traversal

CVE-2026-5210 Overview

A Local File Inclusion (LFI) vulnerability has been identified in SourceCodester Leave Application System version 1.0. This vulnerability affects an unknown component of the application and allows attackers to perform file inclusion attacks by manipulating the page argument. The vulnerability can be exploited remotely over the network without requiring authentication, potentially allowing attackers to read sensitive files, execute arbitrary code, or gain unauthorized access to the underlying system.

Critical Impact

Remote attackers can exploit this file inclusion vulnerability to read sensitive system files, potentially leading to information disclosure, configuration exposure, or further system compromise through code execution.

Affected Products

• SourceCodester Leave Application System 1.0
• PHP/SQLite3-based Leave Application System implementations

Discovery Timeline

• 2026-03-31 - CVE-2026-5210 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-5210

Vulnerability Analysis

This vulnerability is classified as CWE-73 (External Control of File Name or Path), which occurs when the application allows user-controlled input to directly influence file path operations. In the context of the Leave Application System, the page parameter is susceptible to manipulation, enabling attackers to include arbitrary files from the server's file system.

The vulnerability represents a classic Local File Inclusion (LFI) pattern commonly found in PHP applications. When the application processes the page parameter without proper sanitization or validation, an attacker can inject path traversal sequences to access files outside the intended directory structure. This can lead to exposure of sensitive configuration files, source code, or system files such as /etc/passwd on Linux systems.

Root Cause

The root cause of this vulnerability stems from improper input validation on the page parameter. The application fails to adequately sanitize user-supplied input before using it in file operations, such as include(), require(), or similar PHP file handling functions. Without proper validation, path traversal characters (e.g., ../) can be used to navigate the directory structure and include unintended files.

The lack of a whitelist-based approach for acceptable file paths and the absence of input filtering for special characters enables this exploitation vector.

Attack Vector

The attack can be carried out remotely over the network without requiring authentication. An attacker can craft malicious HTTP requests containing manipulated page parameter values to traverse directories and include sensitive files. The exploitation is straightforward and does not require complex attack conditions.

For example, an attacker could modify the page parameter to include path traversal sequences that reference system files or configuration files. The exploit has been publicly disclosed, increasing the risk of widespread exploitation attempts.

Detailed technical analysis of this LFI vulnerability is available in the Medium LFI Analysis writeup. Additional vulnerability details can be found at the VulDB Vulnerability #354346 entry.

Detection Methods for CVE-2026-5210

Indicators of Compromise

• HTTP requests containing path traversal sequences (../, ..%2f, ..%5c) in the page parameter
• Unusual access patterns to sensitive system files such as /etc/passwd, /etc/shadow, or application configuration files
• Web server logs showing requests with encoded traversal characters targeting the Leave Application System
• Error messages in application logs indicating failed file inclusion attempts

Detection Strategies

• Deploy Web Application Firewall (WAF) rules to detect and block path traversal patterns in request parameters
• Monitor HTTP access logs for requests containing ../ sequences or URL-encoded variants in the page parameter
• Implement file integrity monitoring on sensitive system and configuration files
• Configure intrusion detection systems (IDS) to alert on LFI attack signatures

Monitoring Recommendations

• Enable verbose logging for the Leave Application System to capture all parameter values in requests
• Set up alerts for repeated failed file access attempts from single source IPs
• Monitor for unusual file read operations originating from the web application process
• Review web server access logs regularly for suspicious page parameter values

How to Mitigate CVE-2026-5210

Immediate Actions Required

• Remove or disable the SourceCodester Leave Application System from production environments until a patch is available
• Implement strict input validation on the page parameter using a whitelist of allowed values
• Deploy WAF rules to block path traversal attack patterns targeting this application
• Restrict file system permissions for the web server user to limit the impact of successful exploitation

Patch Information

No official patch information is currently available from SourceCodester. Organizations using this application should monitor the SourceCodester Security Resources page for updates. Given the public disclosure of this vulnerability, applying mitigations and considering alternative solutions is strongly recommended.

Workarounds

• Implement a whitelist-based approach that only allows predefined, safe values for the page parameter
• Use PHP's basename() function to strip directory components from user input before file operations
• Disable remote file inclusion by setting allow_url_include = Off in php.ini
• Implement proper access controls and chroot the web application to limit file system access

# PHP configuration hardening example
# Add to php.ini or .htaccess

# Disable remote file inclusion
php_flag allow_url_include Off

# Set open_basedir to restrict file access
php_admin_value open_basedir /var/www/html/leave-application/

# Disable dangerous functions
php_admin_value disable_functions "exec,passthru,shell_exec,system,proc_open,popen"