CVE-2017-17813 in NASM
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there is a use-after-free in the pp_list_one_macro function in asm/preproc.c that will cause a remote denial of service attack, related to mishandling of line-syntax errors.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17813 resides within the Netwide Assembler (NASM) version 2.14rc0, a widely used x86 and x86-64 assembler for Unix-like systems and Windows. This issue manifests as a use-after-free condition that occurs within the pp_list_one_macro function located in the asm/preproc.c source file, representing a critical flaw that can be exploited remotely to execute denial of service attacks. The vulnerability specifically arises from improper handling of line-syntax errors during the preprocessing phase of assembly code compilation, where the assembler fails to properly manage memory allocation and deallocation sequences when processing malformed macro definitions.
The technical nature of this vulnerability stems from a classic memory safety issue categorized under CWE-416, which describes the use of freed memory condition where a program continues to reference memory that has already been freed. In the context of NASM's preprocessing engine, when malformed macro syntax is encountered, the pp_list_one_macro function attempts to process and display error information while simultaneously freeing memory resources that are subsequently accessed during the error reporting process. This creates a scenario where the program may attempt to read from or write to memory that has already been deallocated, leading to unpredictable behavior and potential system instability.
The operational impact of CVE-2017-17813 extends beyond simple system crashes, as it represents a remote denial of service vulnerability that can be triggered by maliciously crafted assembly source files. Attackers can exploit this weakness by submitting specially designed macro definitions that cause the assembler to enter the vulnerable code path, resulting in a crash that prevents legitimate compilation operations from completing successfully. This vulnerability affects the availability of the assembler service and can be particularly problematic in environments where automated build systems or online compilation services rely on NASM for code processing. The issue is particularly concerning in continuous integration environments or web-based assembly tools where untrusted input could be processed without proper sanitization.
Mitigation strategies for this vulnerability require immediate patching of NASM to version 2.14 or later, where the memory management issues have been addressed through proper handling of freed memory references in the preprocessing module. Organizations should implement input validation measures that sanitize assembly source files before processing, particularly focusing on macro definitions and syntax elements that could trigger the vulnerable code path. Additionally, system administrators should consider implementing sandboxing techniques to isolate the assembler process and limit potential impact should exploitation occur. The vulnerability aligns with ATT&CK technique T1499.004, which covers the use of denial of service attacks against applications, and represents a clear example of how memory safety issues in development tools can create security risks that extend beyond the immediate application boundaries into broader system availability concerns.