CVE-2017-15939 in binutils
Summary
by MITRE
dwarf2.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.29, mishandles NULL files in a .debug_line file table, which allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted ELF file, related to concat_filename. NOTE: this issue is caused by an incomplete fix for CVE-2017-15023.
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Analysis
by VulDB Data Team • 01/05/2023
The vulnerability identified as CVE-2017-15939 represents a critical denial of service flaw within the Binary File Descriptor (BFD) library component of GNU Binutils version 2.29. This issue specifically targets the dwarf2.c file which processes .debug_line file tables, creating a scenario where remote attackers can manipulate the system through carefully crafted ELF files. The vulnerability stems from an incomplete remediation of a previously addressed issue, CVE-2017-15023, indicating a regression in the security patching process that leaves systems exposed to potential exploitation. The BFD library serves as a fundamental component for handling various binary file formats, making this vulnerability particularly concerning as it affects core functionality used across numerous security tools and development environments.
The technical flaw manifests when the dwarf2.c implementation fails to properly handle NULL file references within .debug_line file tables during the concat_filename operation. This improper handling results in a NULL pointer dereference condition that causes the application to crash instantly upon encountering the malformed ELF file. The vulnerability operates at the level of binary file parsing where debug information is processed, specifically targeting the debugging line table structures that contain metadata about source code locations within compiled binaries. The flaw occurs because the code does not validate that file pointers remain valid before attempting to access their contents, creating an exploitable path where attacker-controlled input can force the application into an unrecoverable crash state.
The operational impact of this vulnerability extends beyond simple service disruption as it enables remote attackers to systematically crash applications that rely on BFD library functionality for binary analysis. Systems that process untrusted ELF files, such as malware analysis tools, package managers, and security scanning applications, become vulnerable to this attack vector. The nature of the crash means that legitimate applications using the affected library will experience unexpected termination, potentially leading to complete service unavailability. This vulnerability particularly affects environments where automated processing of binary files occurs, as a single malicious file can trigger cascading failures across multiple dependent systems. The remote exploitation aspect means that attackers can trigger this condition without requiring local access, making it a significant threat to networked systems that process external binary content.
Mitigation strategies for CVE-2017-15939 focus primarily on upgrading to patched versions of GNU Binutils where the vulnerability has been properly addressed. Organizations should prioritize updating their systems to versions that include complete fixes for both CVE-2017-15939 and its predecessor CVE-2017-15023, ensuring that the remediation covers all aspects of the file handling logic. Additionally, implementing proper input validation and sanitization measures can help reduce the risk of exploitation by filtering out malformed ELF files before they reach the vulnerable parsing code. Network-level protections such as intrusion detection systems can be configured to monitor for patterns associated with this vulnerability, while application-level sandboxing can limit the damage if exploitation occurs. The vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of how incomplete security patches can create persistent vulnerabilities that require careful attention to ensure comprehensive remediation. This issue also maps to ATT&CK technique T1059 which involves the execution of malicious code through crafted inputs, demonstrating the importance of robust input validation in preventing such exploitation scenarios.