CVE-2022-48303: GNU Tar Use-After-Free Vulnerability

CVE-2022-48303 Overview

GNU Tar through version 1.34 contains a one-byte out-of-bounds read vulnerability that results in the use of uninitialized memory for a conditional jump. The issue occurs in the from_header function within list.c when processing a V7 archive where the mtime field contains approximately 11 whitespace characters. While exploitation to change the flow of control has not been demonstrated, this vulnerability could lead to denial of service conditions through application crashes.

Critical Impact

A local attacker can craft a malicious V7 tar archive that triggers an out-of-bounds read in GNU Tar, potentially causing application crashes and denial of service when a user extracts the archive.

Affected Products

• GNU Tar through version 1.34
• Fedora 37
• Fedora 38

Discovery Timeline

• 2023-01-30 - CVE CVE-2022-48303 published to NVD
• 2025-03-27 - Last updated in NVD database

Technical Details for CVE-2022-48303

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory corruption issue that occurs when GNU Tar processes specially crafted V7 archive headers. The flaw exists in the from_header function located in list.c, which is responsible for parsing archive header information during extraction operations.

When the mtime (modification time) field of a V7 archive header contains approximately 11 whitespace characters, the parsing logic fails to properly validate buffer boundaries. This results in a one-byte out-of-bounds read that accesses uninitialized memory, which is then used in a conditional jump operation. The vulnerability requires local access and user interaction, as a victim must be tricked into extracting a maliciously crafted archive file.

Root Cause

The root cause stems from insufficient bounds checking in the header parsing logic within GNU Tar. The from_header function does not properly validate the length and content of the mtime field when processing V7 archive format headers. When encountering an mtime field padded with excessive whitespace characters, the parser reads beyond the allocated buffer boundary by one byte, accessing uninitialized memory that influences program control flow through conditional jump operations.

Attack Vector

This vulnerability requires local access to the target system. An attacker must craft a malicious V7 format tar archive with a specially constructed mtime field containing approximately 11 whitespace characters. The attack scenario involves distributing this malicious archive to potential victims who would then extract it using a vulnerable version of GNU Tar.

The vulnerability can be triggered through various means:

• Direct command-line extraction: tar -xvf malicious.tar
• Automated archive processing scripts
• Build systems that extract dependencies from tar archives
• Backup restoration operations

The exploitation complexity is low since no special privileges are required, though user interaction is necessary to initiate the archive extraction process. While the vulnerability has not been demonstrated to achieve arbitrary code execution, it can reliably cause denial of service through application crashes.

Detection Methods for CVE-2022-48303

Indicators of Compromise

• Unexpected crashes or segmentation faults when extracting tar archives
• Core dumps generated during tar extraction operations containing references to from_header or list.c
• V7 format tar archives with abnormally long mtime fields or excessive whitespace in header metadata
• Suspicious tar archives received from untrusted sources with unusual header structures

Detection Strategies

• Monitor for GNU Tar process crashes and analyze core dumps for patterns consistent with this vulnerability
• Implement file integrity monitoring to detect modified tar binaries or unexpected archive processing behavior
• Deploy endpoint detection rules to identify extraction of V7 format archives from untrusted sources
• Use static analysis tools to scan incoming tar archives for malformed header fields before extraction

Monitoring Recommendations

• Enable system logging for tar operations and monitor for abnormal termination signals
• Configure crash reporting to capture and alert on GNU Tar segmentation faults
• Implement network monitoring to detect distribution of potentially malicious archive files
• Monitor build and CI/CD systems for unexpected failures during archive extraction phases

How to Mitigate CVE-2022-48303

Immediate Actions Required

• Update GNU Tar to a patched version that addresses this vulnerability
• Review and restrict access to tar archive extraction operations in production environments
• Validate tar archives from untrusted sources before extraction using archive inspection tools
• Consider implementing sandboxed extraction for archives from external sources

Patch Information

GNU has released patches to address this vulnerability. The official bug report and patch submission are available through the GNU Savannah project:

• GNU Bug Report #62387 - Official bug tracking entry
• GNU Patch Submission #10307 - Security patch details

Fedora has also released updated packages for affected versions. Users of Fedora 37 and Fedora 38 should apply the latest security updates through their package manager using dnf update tar.

Workarounds

• Avoid extracting tar archives from untrusted or unknown sources until patching is complete
• Use alternative archive extraction tools that are not affected by this vulnerability when processing untrusted files
• Implement archive validation and inspection procedures before extraction in automated workflows
• Consider running tar extraction operations in containerized or sandboxed environments to limit potential impact

# Update GNU Tar on Fedora systems
sudo dnf update tar

# Verify installed tar version
tar --version

# Alternative: Use archive inspection before extraction
file suspicious_archive.tar
tar -tvf suspicious_archive.tar 2>&1 | head -20