CVE-2021-46174: GNU Binutils Buffer Overflow Vulnerability

CVE-2021-46174 Overview

CVE-2021-46174 is a heap-based buffer overflow vulnerability affecting the bfd_getl32 function in GNU Binutils objdump version 3.37. This memory corruption flaw allows attackers to cause a denial of service condition by crafting malicious input that triggers an out-of-bounds write operation in heap memory.

Critical Impact

This vulnerability can be exploited remotely without authentication to crash the objdump binary analysis tool, potentially disrupting development workflows and automated build systems that rely on Binutils for binary file processing.

Affected Products

• GNU Binutils 3.37 and potentially other versions
• Systems and development environments utilizing objdump for binary analysis
• Build pipelines and CI/CD systems incorporating Binutils utilities

Discovery Timeline

• 2023-08-22 - CVE-2021-46174 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-46174

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), specifically manifesting as a heap-based buffer overflow. The flaw resides in the bfd_getl32 function, which is responsible for reading 32-bit little-endian values from binary files during the object file analysis process.

The vulnerability can be triggered remotely via network-delivered malicious binary files. No privileges or user interaction are required for exploitation, making this a particularly accessible attack vector. While the vulnerability does not allow for data exfiltration or integrity violations, it can reliably cause denial of service by crashing the objdump process.

Root Cause

The root cause of this vulnerability lies in insufficient bounds checking within the bfd_getl32 function when processing binary file data. When objdump parses a specially crafted binary file, the function fails to properly validate buffer boundaries before reading data, leading to heap memory corruption. This out-of-bounds write can corrupt heap metadata or adjacent memory regions, ultimately causing process termination.

Attack Vector

The attack vector for CVE-2021-46174 is network-based, requiring no authentication or special privileges. An attacker can exploit this vulnerability by:

1. Creating a maliciously crafted binary file designed to trigger the buffer overflow
2. Delivering the file to a target system through various means (email attachment, download, repository poisoning)
3. Waiting for the target to analyze the file using objdump, triggering the heap overflow and causing a crash

The vulnerability is particularly concerning in automated environments where binary files are routinely analyzed without manual inspection, such as in CI/CD pipelines, malware analysis sandboxes, or package build systems.

The heap-based buffer overflow occurs when the bfd_getl32 function attempts to read beyond allocated buffer boundaries. In objdump's binary processing workflow, this function is called during the parsing of various binary format structures. A malformed input file can cause the function to access heap memory outside its intended bounds, corrupting heap structures and leading to process termination. Technical details of the vulnerability can be found in the Sourceware Bug Report #28753.

Detection Methods for CVE-2021-46174

Indicators of Compromise

• Unexpected crashes of objdump processes with heap corruption signatures
• Core dumps showing memory access violations in bfd_getl32 or related BFD library functions
• Unusual binary files in processing queues that consistently cause objdump failures
• System logs indicating SIGABRT or SIGSEGV signals from Binutils processes

Detection Strategies

• Monitor objdump and related Binutils processes for abnormal termination patterns
• Implement file integrity monitoring on binary analysis environments to detect malicious input files
• Deploy application-level crash monitoring to identify repeated heap corruption events
• Use AddressSanitizer (ASAN) builds of Binutils in development environments to catch overflow attempts

Monitoring Recommendations

• Enable verbose logging for build systems and CI/CD pipelines using Binutils
• Configure crash reporting mechanisms to capture and analyze objdump failures
• Implement rate limiting on binary file processing to mitigate potential DoS attacks
• Monitor system resource usage for anomalies during binary analysis operations

How to Mitigate CVE-2021-46174

Immediate Actions Required

• Update GNU Binutils to a patched version that addresses the heap overflow in bfd_getl32
• Audit systems to identify all installations of vulnerable Binutils versions
• Restrict network access to systems running objdump on untrusted binary files
• Implement input validation for binary files before processing with objdump

Patch Information

Organizations should update their GNU Binutils installations to versions released after the vulnerability was addressed. Detailed information about the vulnerability and potential fixes can be found in the Sourceware Bug Report #28753. Consult your Linux distribution's security advisories for packaged updates, or compile Binutils from source using the latest stable release from the GNU project.

Workarounds

• Isolate objdump execution in sandboxed environments or containers to limit crash impact
• Implement timeout mechanisms for binary analysis operations to prevent resource exhaustion
• Use alternative binary analysis tools for untrusted files until patching is complete
• Deploy process restart mechanisms to maintain service availability despite crashes

# Configuration example: Running objdump in a restricted environment
# Use firejail or similar sandboxing to isolate objdump execution
firejail --quiet --private --net=none objdump -d suspicious_binary

# Alternative: Use Docker to isolate binary analysis
docker run --rm --read-only -v /path/to/binary:/input:ro binutils-container objdump -d /input/file