CVE-2016-4487 in libiberty
Summary
by MITRE
Use-after-free vulnerability in libiberty allows remote attackers to cause a denial of service (segmentation fault and crash) via a crafted binary, related to "btypevec."
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Analysis
by VulDB Data Team • 08/17/2020
The CVE-2016-4487 vulnerability represents a critical use-after-free flaw within the libiberty library, a component widely utilized in various software development tools and systems. This vulnerability specifically affects the btypevec functionality, which is responsible for handling binary type vectors in the context of binary analysis and processing. The libiberty library serves as a foundational component for numerous GNU tools including the GNU compiler collection and various debugging utilities, making this flaw particularly concerning from a security perspective. The vulnerability stems from improper memory management practices where freed memory blocks are accessed after being deallocated, creating opportunities for malicious exploitation. This type of vulnerability falls under the CWE-416 category, which specifically addresses the use of freed memory, and aligns with the broader class of memory safety issues that have historically led to significant security breaches.
The technical implementation of this vulnerability occurs when a maliciously crafted binary triggers the btypevec processing routine within libiberty. During normal operation, the library allocates memory for binary type vector structures to store metadata about binary files. However, when processing malformed input, the memory management logic fails to properly track the lifecycle of these allocated structures. This results in a situation where the program attempts to access memory that has already been freed, leading to segmentation faults and subsequent program crashes. The vulnerability is particularly insidious because it can be triggered remotely through the processing of untrusted binary files, making it a significant concern for systems that handle binary data from external sources. The exploitation mechanism relies on the attacker crafting a specific binary payload that causes the library to enter an inconsistent state where freed memory is accessed, demonstrating the classic use-after-free attack pattern.
The operational impact of CVE-2016-4487 extends beyond simple denial of service conditions, as it can potentially be leveraged for more sophisticated attacks depending on the system context. While the immediate effect manifests as segmentation faults and crashes, the underlying memory corruption vulnerability creates opportunities for attackers to potentially execute arbitrary code or escalate privileges in certain scenarios. Systems that rely heavily on libiberty for binary analysis, such as static analysis tools, debuggers, and compiler frontends, become particularly vulnerable. The vulnerability affects a broad range of applications including GNU binutils, various development environments, and security analysis tools that utilize the GNU toolchain. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique involving network denial of service, and could potentially be extended to T1059.007 for command execution if the memory corruption leads to code execution. The widespread adoption of libiberty across multiple software domains means that exploitation of this vulnerability could impact numerous systems and applications that process binary data.
Mitigation strategies for CVE-2016-4487 require immediate patching of affected systems and software components. The most effective approach involves upgrading to versions of libiberty that contain proper memory management fixes, typically released as part of the GNU toolchain updates. System administrators should prioritize patching all instances of affected software, particularly those handling untrusted binary inputs. Additionally, implementing input validation and sanitization measures can help reduce the attack surface by preventing malformed binaries from reaching the vulnerable code paths. Network segmentation and access controls should be enforced to limit exposure of systems that process binary data from external sources. The vulnerability highlights the importance of proper memory management practices and the need for comprehensive testing of memory handling code, especially in widely used library components. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to make exploitation more difficult. Regular security audits of critical library dependencies and maintaining up-to-date vulnerability databases are essential practices to prevent similar issues from affecting systems in the future. The vulnerability serves as a reminder of the critical importance of memory safety in system components that are widely distributed and integrated into numerous applications across the software ecosystem.