CVE-2022-0530: Unzip Project Unzip RCE Vulnerability

CVE-2022-0530 Overview

A heap out-of-bounds write vulnerability has been identified in Unzip, the widely-used archive extraction utility. The flaw occurs during the conversion of a wide string to a local string, causing an out-of-bounds write to heap memory. This vulnerability allows an attacker to craft a specially designed zip file that, when processed by the affected unzip utility, can lead to application crashes or potentially arbitrary code execution.

Critical Impact

Processing a maliciously crafted ZIP file can trigger a heap out-of-bounds write, potentially leading to denial of service through application crashes or code execution on affected systems including Linux distributions and macOS.

Affected Products

• Unzip Project Unzip 6.0
• Red Hat Enterprise Linux 8.0
• Fedora 35
• Apple macOS and Mac OS X (multiple versions including 10.15.7 with various security updates)
• Debian Linux 10.0 and 11.0

Discovery Timeline

• February 9, 2022 - CVE-2022-0530 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-0530

Vulnerability Analysis

The vulnerability resides in the wide string to local string conversion functionality within Unzip. When processing filenames or other string data from ZIP archives, the utility performs character encoding conversion operations. During this conversion process, improper bounds checking allows writes to occur beyond the allocated heap buffer boundaries.

The attack requires local access with user interaction—specifically, a victim must extract a maliciously crafted ZIP archive. While this limits the attack surface compared to network-exploitable vulnerabilities, the ubiquitous nature of ZIP file handling across desktop and server environments makes this a significant concern. The vulnerability primarily impacts system availability through crashes, though code execution scenarios cannot be ruled out depending on heap layout and system configuration.

Root Cause

The root cause is inadequate validation of string lengths and buffer boundaries during wide character to multibyte character conversion. When processing ZIP entries containing specially crafted filenames or metadata with wide character strings, the conversion routine fails to properly calculate the required buffer size, resulting in heap memory corruption beyond allocated boundaries.

Attack Vector

Exploitation requires delivering a malicious ZIP file to a victim and convincing them to extract it using an affected version of unzip. Attack scenarios include:

1. Email-based delivery of malicious ZIP attachments
2. Hosting malicious archives on web servers for download
3. Placing malicious ZIP files on shared network drives or cloud storage
4. Supply chain attacks through compromised software distribution archives

The vulnerability is triggered during the extraction process when unzip attempts to convert wide character strings (such as Unicode filenames) to local character encoding. The malformed string data causes the heap out-of-bounds write, potentially corrupting adjacent heap metadata or application data structures.

A proof-of-concept demonstrating this vulnerability is available in the GitHub PoC Repository for security research purposes.

Detection Methods for CVE-2022-0530

Indicators of Compromise

• Unexpected crashes or segmentation faults in the unzip process during archive extraction
• Core dump files generated by unzip with heap corruption signatures
• Anomalous ZIP files with unusually long or malformed Unicode filenames in metadata

Detection Strategies

• Monitor for unzip process crashes and collect crash dumps for analysis
• Implement file integrity monitoring on systems where unzip is commonly used
• Deploy endpoint detection rules to identify suspicious ZIP file processing activities
• Utilize memory protection mechanisms (ASLR, heap guards) to detect exploitation attempts

Monitoring Recommendations

• Enable process crash logging and alerting for unzip and related archive utilities
• Monitor for unusual patterns of ZIP file extraction, particularly from untrusted sources
• Implement sandboxing for archive extraction operations in automated workflows
• Review system logs for repeated unzip failures that may indicate exploitation attempts

How to Mitigate CVE-2022-0530

Immediate Actions Required

• Update unzip to the latest patched version available for your distribution
• Apply vendor security updates from Apple, Red Hat, Debian, or Fedora as applicable
• Restrict extraction of ZIP files from untrusted sources until patches are applied
• Consider using alternative archive utilities with security mitigations enabled

Patch Information

Security patches addressing this vulnerability have been released by multiple vendors:

• Apple: Security updates documented in HT213255, HT213256, and HT213257
• Debian: DSA-5202 and related LTS announcements
• Red Hat: Tracked via Bugzilla #2051395
• Gentoo: GLSA 202310-17

Apply the appropriate patches for your operating system and distribution immediately.

Workarounds

• Avoid extracting ZIP files from untrusted or unknown sources
• Use alternative archive utilities (such as 7z or bsdtar) that may not be affected
• Implement file scanning and validation before processing ZIP archives
• Run archive extraction in isolated environments or containers with limited privileges

# Check installed unzip version on Linux
unzip -v | head -1

# Update unzip on Debian/Ubuntu systems
sudo apt update && sudo apt install --only-upgrade unzip

# Update unzip on Red Hat/Fedora systems
sudo dnf update unzip