CVE-2018-6759 in binutils
Summary
by MITRE
The bfd_get_debug_link_info_1 function in opncls.c in the Binary File Descriptor (BFD) library (aka libbfd), as distributed in GNU Binutils 2.30, has an unchecked strnlen operation. Remote attackers could leverage this vulnerability to cause a denial of service (segmentation fault) via a crafted ELF file.
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Analysis
by VulDB Data Team • 02/02/2021
The vulnerability identified as CVE-2018-6759 resides within the Binary File Descriptor (BFD) library, specifically in the bfd_get_debug_link_info_1 function located in the opncls.c file. This library component is part of GNU Binutils 2.30 and serves as a critical foundation for binary file manipulation and analysis across various system tools. The flaw manifests as an unchecked strnlen operation that fails to properly validate input parameters, creating a potential pathway for malicious exploitation. When processing specially crafted ELF files, the function attempts to calculate string lengths without adequate bounds checking, leading to unpredictable behavior in memory access patterns.
The technical implementation of this vulnerability stems from the absence of proper input validation within the debug link information parsing mechanism. The strnlen function, which is designed to calculate the length of a string up to a maximum number of characters, is invoked without ensuring that the input buffer contains valid data or that the maximum length parameter remains within acceptable bounds. This unchecked operation creates a scenario where malformed ELF files can trigger memory corruption conditions that ultimately result in segmentation faults. The vulnerability is particularly concerning because it operates at a low-level library function that is frequently invoked by various system utilities and security tools that process binary files.
From an operational perspective, this vulnerability presents a significant denial of service risk that can be exploited remotely through the careful crafting of ELF files. Attackers can leverage this flaw by preparing specially designed binary files that, when processed by any application utilizing the affected BFD library, will trigger segmentation faults and subsequent system crashes. The impact extends beyond simple service disruption as it can affect critical system components that rely on binary file analysis, including security scanners, debuggers, and system monitoring tools. The vulnerability's remote exploitation capability means that systems processing untrusted binary content could become compromised, potentially allowing for more sophisticated attack vectors if combined with other vulnerabilities.
The weakness aligns with CWE-126, which describes "Buffer Over-read" conditions where an application reads data past the end of a buffer, and potentially with CWE-121, which covers "Stack-based Buffer Overflow" scenarios. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for the execution of malicious code through file processing and T1499.004 for the disruption of services through denial of service attacks. The exploitability of this vulnerability is enhanced by the fact that it can be triggered through common file processing operations that occur in automated systems, making it particularly dangerous in environments where binary file analysis is routine. Mitigation strategies should focus on implementing proper bounds checking, applying the patched version of GNU Binutils, and employing input validation measures that prevent malformed binary content from reaching vulnerable library functions.
This vulnerability demonstrates the critical importance of proper memory management and input validation in low-level system libraries. The BFD library's role as a foundational component in binary file processing means that flaws within its implementation can have cascading effects across numerous security and system administration tools. Organizations should prioritize updating to patched versions of GNU Binutils while implementing additional defensive measures such as sandboxing file processing operations and deploying intrusion detection systems that can identify attempts to exploit such vulnerabilities. The incident underscores the necessity of rigorous code review processes for system libraries that handle untrusted input, particularly in security-sensitive environments where reliability and robustness are paramount requirements for maintaining system integrity and availability.