CVE-2018-20712 in binutils
Summary
by MITRE
A heap-based buffer over-read exists in the function d_expression_1 in cp-demangle.c in GNU libiberty, as distributed in GNU Binutils 2.31.1. A crafted input can cause segmentation faults, leading to denial-of-service, as demonstrated by c++filt.
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Analysis
by VulDB Data Team • 03/06/2025
The vulnerability identified as CVE-2018-20712 represents a critical heap-based buffer over-read flaw within the GNU libiberty library, specifically in the cp-demangle.c component that is part of the GNU Binutils 2.31.1 distribution. This issue manifests when the d_expression_1 function processes malformed input data, creating a condition where the program attempts to read memory beyond the allocated buffer boundaries. The flaw occurs during the demangling process of C++ symbols, which is a fundamental operation performed by tools like c++filt that translate mangled symbol names into human-readable formats. The vulnerability is particularly concerning because it affects core components of the GNU toolchain that are widely used in software development and system administration environments.
The technical implementation of this buffer over-read stems from inadequate input validation within the demangling function's parsing logic. When the d_expression_1 function encounters crafted input, it fails to properly bounds-check memory accesses during the symbol parsing process, allowing an attacker to manipulate the program flow through carefully constructed input sequences. This vulnerability operates at the heap memory level, meaning the over-read occurs in dynamically allocated memory regions rather than stack-based buffers, making it more difficult to detect and exploit. The flaw can be triggered by providing malformed C++ symbol names to the c++filt utility, which then processes these inputs through the vulnerable demangling code path. According to CWE classification, this represents a CWE-125: Out-of-Bounds Read vulnerability that specifically affects heap memory management operations.
The operational impact of CVE-2018-20712 extends beyond simple denial-of-service conditions, as it can potentially lead to more severe consequences in environments where the affected tools are used in automated processing pipelines or security-sensitive contexts. When exploited, the buffer over-read causes segmentation faults that terminate the c++filt process, effectively preventing symbol demangling operations from completing successfully. This denial-of-service condition can be particularly disruptive in build environments, debugging workflows, or automated testing systems that rely on proper symbol resolution. The vulnerability aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, where adversaries target application stability through memory corruption vulnerabilities. In practical scenarios, this flaw could be leveraged by attackers to disrupt development processes, prevent software compilation, or create conditions that mask more sophisticated attacks by consuming system resources through repeated exploitation attempts.
Mitigation strategies for CVE-2018-20712 should focus on immediate patching of affected GNU Binutils installations to version 2.32 or later, where the buffer over-read vulnerability has been addressed through proper input validation and bounds checking. System administrators should prioritize updating all development environments, build servers, and automated systems that utilize c++filt or related symbol demangling tools. Additionally, implementing input sanitization measures in applications that process user-provided symbol names can provide defense-in-depth protection against similar vulnerabilities. The fix implemented by the GNU project involved strengthening the bounds checking mechanisms within the cp-demangle.c function to prevent memory access violations when processing malformed input sequences. Organizations should also consider monitoring for unusual c++filt process termination patterns or segmentation fault occurrences that might indicate exploitation attempts, as these could serve as early warning indicators of potential attacks targeting this vulnerability.