CVE-2017-17817 in NASM
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there is a use-after-free in pp_verror in asm/preproc.c that will cause a remote denial of service attack.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17817 resides within the Netwide Assembler (NASM) version 2.14rc0, a widely used assembler for x86 and x86-64 architectures. This flaw manifests as a use-after-free condition in the pp_verror function located within the asm/preproc.c source file, representing a critical memory safety issue that can be exploited to execute remote denial of service attacks. The vulnerability occurs during the preprocessing phase of assembly code compilation, where improper memory management leads to the execution of code against freed memory locations, potentially causing unpredictable behavior and system instability.
The technical implementation of this vulnerability involves the pp_verror function's handling of error conditions within NASM's preprocessing pipeline. When certain malformed input or specific error scenarios are encountered, the function attempts to reference memory that has already been deallocated, creating a use-after-free condition. This memory corruption can occur when the preprocessor processes malformed assembly directives or encounters specific combinations of macro definitions and conditional compilation directives. The flaw is particularly concerning because it operates within the core preprocessing functionality that is invoked during normal assembly operations, making it accessible through legitimate assembly input processing.
From an operational impact perspective, this vulnerability enables remote attackers to trigger denial of service conditions by crafting specific assembly input that will cause NASM to execute the use-after-free scenario. The remote attack vector means that an attacker could potentially compromise systems that rely on NASM for automated assembly processing, including build servers, continuous integration environments, or any system that processes untrusted assembly code. The vulnerability could be exploited in scenarios where NASM is used as part of automated toolchains or web-based assembly processing services, leading to service disruption and potential system crashes.
The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software implementations. From an adversarial perspective, this flaw maps to ATT&CK technique T1499.004, which involves network denial of service attacks. The exploitability of this vulnerability demonstrates the importance of proper memory management in compiler toolchains, as these tools often handle untrusted input from multiple sources. The remote nature of the attack means that systems processing assembly code from external sources are particularly vulnerable, making this a significant concern for automated build environments and online assembly processing services.
Mitigation strategies for CVE-2017-17817 should focus on immediate patching of NASM to version 2.14 or later, which contains the necessary memory management fixes. Organizations should also implement input validation measures when processing assembly code, particularly in automated environments where untrusted inputs may be processed. Additional protective measures include deploying sandboxed environments for assembly processing, implementing strict input sanitization procedures, and monitoring for unusual resource consumption patterns that might indicate exploitation attempts. The vulnerability underscores the critical need for memory safety practices in development tools, as these components often serve as foundational elements in software development pipelines and can be targeted for system disruption through carefully crafted inputs.