CVE-2023-52169: 7-Zip Information Disclosure Vulnerability

CVE-2023-52169 Overview

CVE-2023-52169 is an out-of-bounds read vulnerability in the NtfsHandler.cpp NTFS handler component of 7-Zip versions prior to 24.01. This memory safety flaw allows an attacker to read beyond the intended buffer boundaries, potentially exposing sensitive data from adjacent memory regions. The bytes read beyond the buffer are presented as part of a filename listed in the file system image, creating an information disclosure vector.

Critical Impact

Attackers can exploit this vulnerability in web-service environments where untrusted users upload files for server-side extraction, potentially leaking sensitive memory contents through malformed NTFS images.

Affected Products

• 7-Zip versions before 24.01
• 7zz (7-Zip for Linux/macOS) versions before 24.01
• Systems using 7-Zip for server-side archive extraction

Discovery Timeline

• 2024-07-03 - CVE-2023-52169 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2023-52169

Vulnerability Analysis

This vulnerability falls under CWE-125 (Out-of-Bounds Read), a memory corruption issue that occurs when the application reads data from a location outside the bounds of the intended buffer. In the context of 7-Zip's NTFS handler, the vulnerability manifests during the parsing of NTFS filesystem images contained within archives.

The flaw is particularly dangerous in server-side deployment scenarios where 7-Zip is used to automatically extract user-uploaded archives. An attacker can craft a malicious NTFS image that triggers the out-of-bounds read condition, causing the application to read memory beyond the allocated buffer. This leaked memory content is then erroneously interpreted as part of a filename and exposed through the extraction process.

The network-accessible nature of this vulnerability means remote attackers can exploit it without authentication by simply uploading a specially crafted archive to a vulnerable web service. The attack requires no user interaction beyond the automated extraction process.

Root Cause

The root cause lies in improper bounds checking within the NtfsHandler.cpp file when processing NTFS filesystem metadata. The NTFS handler fails to properly validate the length of filename entries before reading them from the buffer, allowing reads to extend past the allocated memory region. This insufficient input validation enables an attacker to craft NTFS images with malformed filename length fields that cause the parser to read arbitrary amounts of memory beyond the intended boundary.

Attack Vector

The attack vector leverages the network-accessible file upload functionality present in many web applications that use 7-Zip for server-side archive extraction. An attacker uploads a malicious archive containing a specially crafted NTFS filesystem image with manipulated filename length fields. When 7-Zip processes the archive, the NTFS handler reads beyond the intended buffer, incorporating leaked memory contents into the displayed or extracted filename. This enables the attacker to exfiltrate sensitive data that may reside in adjacent memory locations, including configuration data, cryptographic material, or other user information.

The vulnerability mechanism involves crafting a malicious NTFS image with manipulated metadata fields that cause the parser to read beyond allocated memory boundaries. Technical details are available in the DFIR Analysis on 7-Zip Vulnerabilities and the SourceForge 7-Zip Bug Report.

Detection Methods for CVE-2023-52169

Indicators of Compromise

• Unusually long or malformed filenames appearing in extracted archive contents
• Archive files with suspicious NTFS filesystem images embedded within them
• Extraction operations producing filenames containing non-printable or unexpected binary characters
• Abnormal memory access patterns in 7-Zip processes during archive extraction

Detection Strategies

• Monitor file extraction operations for anomalous filename lengths or content patterns
• Implement file type validation on uploaded archives before server-side extraction
• Deploy memory protection mechanisms (ASLR, DEP) to limit information disclosure impact
• Use application-level monitoring to detect 7-Zip processes accessing memory regions outside normal boundaries

Monitoring Recommendations

• Log all archive extraction operations with detailed filename output analysis
• Implement alerting for extracted filenames exceeding reasonable length thresholds
• Monitor for repeated extraction attempts from the same source that may indicate exploitation probing
• Track 7-Zip version deployments across infrastructure to identify vulnerable instances

How to Mitigate CVE-2023-52169

Immediate Actions Required

• Upgrade 7-Zip to version 24.01 or later immediately on all affected systems
• Audit web applications and services that use 7-Zip for server-side archive extraction
• Implement input validation to restrict archive types processed by vulnerable 7-Zip versions
• Consider temporarily disabling NTFS image extraction if upgrading is not immediately possible

Patch Information

The vulnerability has been addressed in 7-Zip version 24.01 and later. Organizations should prioritize upgrading all 7-Zip installations, particularly those used in server-side automated extraction scenarios. Additional security advisories have been published by NetApp and discussed in the Openwall OSS Security mailing list.

Workarounds

• Disable server-side extraction of archives containing NTFS filesystem images until patching is complete
• Implement strict file type allowlisting for uploaded archives, rejecting unknown or suspicious formats
• Run 7-Zip extraction processes in sandboxed or containerized environments to limit information disclosure impact
• Deploy web application firewalls (WAF) with rules to inspect and filter potentially malicious archive uploads

# Verify 7-Zip version and upgrade if necessary
7z --version
# Expected output should show version 24.01 or higher

# For package manager installations (example for Debian/Ubuntu)
sudo apt update && sudo apt install 7zip

# Restrict NTFS handling via extraction options when processing untrusted files
7z x -tzip archive.zip  # Force specific archive type to avoid NTFS parsing