CVE-2018-19214 in Netwide Assembler
Summary
by MITRE
Netwide Assembler (NASM) 2.14rc15 has a heap-based buffer over-read in expand_mmac_params in asm/preproc.c for insufficient input.
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Analysis
by VulDB Data Team • 06/05/2023
The vulnerability identified as CVE-2018-19214 affects Netwide Assembler version 2.14rc15, a widely used assembler for x86 and x86-64 architectures. This issue manifests as a heap-based buffer over-read within the expand_mmac_params function located in the asm/preproc.c source file. The flaw occurs when processing insufficient input data, creating a condition where the assembler attempts to read beyond the allocated memory boundaries. This type of vulnerability represents a critical security concern as it can potentially lead to arbitrary code execution or system instability during the assembly process.
The technical implementation of this vulnerability stems from inadequate input validation within the macro processing subsystem of NASM. When the preprocessor encounters malformed or incomplete macro parameters, the expand_mmac_params function fails to properly bounds-check memory accesses before reading data from heap-allocated buffers. This particular flaw aligns with CWE-125, which describes out-of-bounds read conditions in software systems. The vulnerability demonstrates characteristics consistent with heap corruption issues that can be exploited through carefully crafted input sequences that trigger the problematic code path during macro expansion.
From an operational standpoint, this vulnerability poses significant risks to development environments and build systems that rely on NASM for compiling assembly code. Attackers could potentially exploit this flaw by providing malicious input to the assembler, which might result in denial of service conditions, information disclosure, or in more sophisticated scenarios, arbitrary code execution. The impact extends beyond simple compilation failures as the vulnerability affects the core preprocessing functionality that handles macro expansion, a fundamental feature used extensively in assembly programming. This makes the vulnerability particularly dangerous in automated build environments where assembly code is processed without manual oversight.
The exploitation of this vulnerability requires understanding of the assembler's macro processing mechanisms and careful crafting of input data that triggers the specific code path. According to ATT&CK framework category T1059, this represents a software exploitation technique targeting compiler or assembler tools. Mitigation strategies should include immediate patching of NASM to version 2.14 or later where the issue has been resolved through proper input validation and memory bounds checking. Organizations should also implement input sanitization measures for any assembly code processing pipelines and consider runtime protections such as address space layout randomization and stack canaries to reduce exploitability. Additionally, security monitoring should be enhanced to detect unusual patterns in assembly processing that might indicate exploitation attempts.