CVE-2021-47921: Free Photo & Video Vault Path Traversal

CVE-2021-47921 Overview

CVE-2021-47921 is a directory traversal vulnerability affecting Free Photo & Video Vault version 0.0.2. This mobile application vulnerability allows remote attackers to manipulate application path requests via malicious web requests, enabling unauthorized access to sensitive system files. The flaw exists in the application's web-based WiFi transfer functionality, where insufficient input validation permits attackers to escape the intended directory structure and traverse to arbitrary system locations.

Critical Impact

Remote attackers can exploit this directory traversal vulnerability without special privileges to retrieve environment variables, access unauthorized system paths, and potentially expose sensitive user data stored on the device.

Affected Products

• Free Photo & Video Vault version 0.0.2
• iOS devices running the vulnerable application with WiFi transfer enabled

Discovery Timeline

• 2026-02-01 - CVE-2021-47921 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2021-47921

Vulnerability Analysis

This directory traversal vulnerability (CWE-22) exists within the web server component of Free Photo & Video Vault that facilitates WiFi-based file transfers. The application exposes a local web server when users enable the WiFi transfer feature, intended to allow convenient file management from a browser. However, the implementation fails to properly sanitize user-supplied path parameters in HTTP requests.

When processing file access requests, the application does not adequately validate or canonicalize the requested path, allowing attackers to include directory traversal sequences (such as ../) in their requests. This enables navigation outside the application's intended file sandbox and into sensitive areas of the device's filesystem.

The network-accessible nature of this vulnerability means any attacker on the same local network as the victim can exploit it without requiring authentication or elevated privileges. The impact is primarily confidentiality-focused, enabling unauthorized disclosure of system files, environment variables, and potentially sensitive user data.

Root Cause

The root cause of CVE-2021-47921 is improper input validation (CWE-22: Improper Limitation of a Pathname to a Restricted Directory). The application's web server component fails to sanitize directory traversal sequences from user-supplied path parameters before using them in filesystem operations. Without proper path canonicalization and boundary checking, malicious requests containing sequences like ../ can escape the application's document root and access arbitrary filesystem locations.

Attack Vector

The attack is conducted remotely over the network when the victim has enabled the WiFi transfer feature. An attacker connected to the same local network can send crafted HTTP requests to the application's web server, embedding directory traversal sequences in the file path parameter. This allows the attacker to:

1. Navigate outside the application's intended directory structure
2. Access sensitive system configuration files
3. Retrieve environment variables that may contain secrets
4. Read other application data stored on the device

The attack requires no authentication and can be performed by any attacker with network access to the target device while the WiFi transfer feature is active. The vulnerability is exploited through standard HTTP requests with manipulated path components that include traversal sequences to reach parent directories and access restricted system paths.

Detection Methods for CVE-2021-47921

Indicators of Compromise

• HTTP requests to the application's web server containing ../ or encoded directory traversal sequences (e.g., %2e%2e%2f)
• Access logs showing requests for system files outside the application's document root
• Unusual network connections to the device on the WiFi transfer port from untrusted hosts
• Evidence of unauthorized file read operations targeting system configuration paths

Detection Strategies

• Monitor network traffic for HTTP requests containing path traversal patterns targeting mobile device web servers
• Implement intrusion detection rules to flag requests with multiple consecutive ../ sequences or URL-encoded equivalents
• Review application logs for failed or successful file access attempts to paths outside expected directories
• Deploy network segmentation to isolate untrusted devices from those running vulnerable applications

Monitoring Recommendations

• Enable verbose logging on network segments where mobile devices operate with WiFi transfer features
• Implement network-based anomaly detection for unusual file access patterns from mobile web servers
• Monitor for reconnaissance activity such as sequential path probing attempts
• Alert on any requests attempting to access known sensitive system paths like /etc/ or environment variable locations

How to Mitigate CVE-2021-47921

Immediate Actions Required

• Disable the WiFi transfer feature in Free Photo & Video Vault immediately when not actively in use
• Avoid using the WiFi transfer feature on untrusted networks
• Consider uninstalling the vulnerable application version 0.0.2 until a patched version is available
• Ensure mobile devices are only connected to trusted, secured networks when using file transfer features

Patch Information

No official patch information is currently available from the vendor for this vulnerability. Users should monitor the Apple App Store listing for application updates. Additional technical details are available from the VulnCheck Security Advisory and Vulnerability Lab Report #2271.

Workarounds

• Keep the WiFi transfer feature disabled at all times unless absolutely necessary
• When WiFi transfer must be used, operate only on isolated, trusted networks without other untrusted devices
• Use alternative secure file transfer methods such as encrypted cloud storage or direct USB connections
• Enable device firewall features if available to restrict incoming connections to the application's web server port
• Consider network-level controls to limit which devices can communicate with mobile devices running vulnerable applications

# Network monitoring example - detect traversal attempts
# Monitor for path traversal patterns in HTTP traffic
tcpdump -i any -A 'tcp port 80 or tcp port 8080' | grep -E '(\.\./|%2e%2e%2f|%252e%252e%252f)'