CVE-2018-20657 in libiberty
Summary
by MITRE
The demangle_template function in cplus-dem.c in GNU libiberty, as distributed in GNU Binutils 2.31.1, has a memory leak via a crafted string, leading to a denial of service (memory consumption), as demonstrated by cxxfilt, a related issue to CVE-2018-12698.
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Analysis
by VulDB Data Team • 06/22/2023
The vulnerability identified as CVE-2018-20657 resides within the GNU libiberty library, specifically in the demangle_template function located in cplus-dem.c. This function serves as a critical component in the demangling process of C++ symbol names, which is essential for tools like cxxfilt that are used to convert mangled symbol names back into human-readable form. The issue manifests when processing crafted input strings that trigger improper memory management within the demangle_template function, creating a condition where allocated memory is not properly released during the demangling operation. The vulnerability affects GNU Binutils 2.31.1, making it particularly concerning as this version was widely distributed and used in various development and system administration environments.
The technical flaw represents a classic memory leak scenario where the demangle_template function fails to properly deallocate memory resources when encountering malformed or specially crafted input strings. This occurs during the processing of C++ template demangling operations, where the function recursively handles complex symbol structures. The vulnerability is particularly insidious because it can be triggered through normal usage of the cxxfilt utility, which is commonly employed in debugging, reverse engineering, and system analysis tasks. When exploited, the function continues to allocate memory without proper cleanup, leading to progressive memory consumption that can eventually exhaust system resources and result in denial of service conditions.
The operational impact of this vulnerability extends beyond simple resource exhaustion, as it affects the reliability and stability of systems that depend on GNU Binutils for symbol processing. Attackers can exploit this weakness by providing malicious input to cxxfilt or other tools that utilize the vulnerable libiberty library, causing memory consumption to grow indefinitely until system resources are depleted. This makes the vulnerability particularly dangerous in environments where these tools are used in automated processes or where they might be exposed to untrusted input from external sources. The vulnerability is related to CVE-2018-12698, indicating a pattern of similar memory management issues within the same codebase, suggesting systemic problems in how template demangling operations handle memory allocation and deallocation. This weakness aligns with CWE-401, which addresses improper deallocation of memory, and falls under the ATT&CK technique T1499.001 for resource exhaustion, as it specifically targets memory consumption as the primary attack vector.
The vulnerability demonstrates a fundamental flaw in the memory management practices within the GNU libiberty library's demangling functions. The recursive nature of template processing combined with inadequate memory cleanup mechanisms creates a perfect storm for memory leaks that can be easily exploited through crafted input strings. The issue is particularly concerning because it affects widely used system tools and can be triggered without requiring special privileges or complex attack vectors. System administrators and developers should consider the broader implications of this vulnerability, as it not only impacts individual tools but can potentially affect entire build systems, debugging environments, and automated analysis pipelines that rely on proper symbol demangling functionality. The recommended mitigation involves updating to patched versions of GNU Binutils where the memory leak has been corrected, ensuring that all memory allocations within the demangle_template function are properly managed and deallocated. Additionally, input validation and sanitization measures should be implemented when processing symbol strings to prevent exploitation of this vulnerability in environments where updated software cannot be immediately deployed.