CVE-2022-23935: ExifTool Command Injection Vulnerability

CVE-2022-23935 Overview

CVE-2022-23935 is a command injection vulnerability discovered in ExifTool, a popular Perl library and command-line tool used for reading, writing, and editing metadata in image, audio, and video files. The vulnerability exists in lib/Image/ExifTool.pm in versions prior to 12.38, where improper handling of a filename check ($file =~ /\\|$/) allows attackers to inject and execute arbitrary system commands.

Critical Impact

Successful exploitation of this vulnerability enables attackers to execute arbitrary commands on the target system by crafting malicious filenames, potentially leading to complete system compromise.

Affected Products

• ExifTool versions prior to 12.38
• Applications and services that integrate ExifTool for metadata processing
• Systems processing untrusted image files through ExifTool

Discovery Timeline

• 2022-01-25 - CVE CVE-2022-23935 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-23935

Vulnerability Analysis

The vulnerability stems from insufficient input validation in ExifTool's file handling mechanism. When processing filenames, the application uses a regex pattern to check for pipe characters at the end of filenames ($file =~ /\\|$/). However, this check is improperly implemented, allowing attackers to bypass the security control and inject shell commands through specially crafted filenames.

ExifTool processes metadata from various file types and is commonly integrated into web applications, content management systems, and file processing pipelines. When a malicious filename containing shell metacharacters is processed, the command injection occurs during the file open operation, as Perl's two-argument open() function interprets certain characters as shell commands.

The vulnerability is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command), indicating that user-controlled input is being passed to a system shell without adequate sanitization.

Root Cause

The root cause lies in the flawed regex pattern used to detect potentially dangerous filenames. The pattern $file =~ /\\|$/ was intended to prevent command execution by blocking filenames ending with a pipe character. However, the implementation fails to account for other shell metacharacters and injection techniques that can bypass this check, particularly when combined with specific character sequences that evade the pattern matching.

Attack Vector

Exploitation requires local access and user interaction, where an attacker must convince a user or automated system to process a maliciously crafted file. The attack vector typically involves:

1. Crafting a filename containing embedded shell commands
2. Delivering the malicious file to a target system
3. Having the file processed by ExifTool (either manually by a user or automatically by an application)

When the malicious file is processed, the embedded commands execute with the privileges of the ExifTool process. This vulnerability is particularly dangerous in environments where ExifTool is used to automatically process uploaded files, such as image galleries, content management systems, or media processing pipelines.

For technical details on the exploitation mechanism, see the GitHub Gist PoC published by security researchers.

Detection Methods for CVE-2022-23935

Indicators of Compromise

• Unusual filenames containing pipe characters (|), semicolons (;), or backticks in image directories
• Unexpected child processes spawned by ExifTool or Perl interpreter processes
• Command execution patterns in process monitoring logs associated with metadata extraction operations
• Anomalous network connections or file system modifications following image file processing

Detection Strategies

• Monitor process creation events for suspicious child processes spawned by exiftool or perl processes
• Implement file upload filtering to detect malicious filename patterns before processing
• Enable command-line auditing to capture full command arguments passed to ExifTool
• Deploy endpoint detection rules to identify command injection attempts targeting metadata processing tools

Monitoring Recommendations

• Configure logging for all ExifTool invocations, including full filename arguments
• Implement file integrity monitoring on systems running ExifTool in automated workflows
• Monitor for unusual process trees where perl or exiftool spawn unexpected shell commands
• Review application logs for errors or anomalies during metadata extraction operations

How to Mitigate CVE-2022-23935

Immediate Actions Required

• Upgrade ExifTool to version 12.38 or later immediately
• Audit systems for ExifTool installations and verify version numbers using exiftool -ver
• Review logs for any suspicious file processing activities that may indicate prior exploitation attempts
• Implement input validation on filenames before passing them to ExifTool

Patch Information

The ExifTool project has released version 12.38 which addresses this command injection vulnerability. The fix involves improved handling of the filename regex check to properly sanitize potentially dangerous input. The security patch can be reviewed in the official commit on GitHub.

Organizations should upgrade to ExifTool 12.38 or later through their package manager or by downloading directly from the official ExifTool website.

Workarounds

• Implement strict filename validation and sanitization before processing files with ExifTool
• Run ExifTool in a sandboxed environment with restricted privileges and limited system access
• Use ExifTool's -stay_open mode with careful input handling to reduce attack surface
• Consider using containerized deployments to isolate ExifTool processing from the host system

# Verify ExifTool version and upgrade if necessary
exiftool -ver

# On Debian/Ubuntu systems, upgrade via package manager
sudo apt update && sudo apt install libimage-exiftool-perl

# For manual installation, download latest version from official source
# and verify integrity before installation