CVE-2017-17815 in NASM
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there is an illegal address access in is_mmacro() in asm/preproc.c that will cause a remote denial of service attack, because of a missing check for the relationship between minimum and maximum parameter counts.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17815 resides within the Netwide Assembler (NASM) version 2.14rc0, a widely used assembler for x86 and x86-64 architectures. This flaw manifests as an illegal address access condition within the is_mmacro() function located in the asm/preproc.c source file, representing a critical security weakness that can be exploited remotely to cause system disruption. The vulnerability specifically targets the preprocessor component of NASM, which handles macro processing and parameter validation during assembly operations.
The technical root cause of this vulnerability stems from an inadequate validation mechanism within the macro parameter handling logic. When processing macro definitions, the is_mmacro() function fails to properly verify the relationship between minimum and maximum parameter counts specified in macro declarations. This missing validation check creates a scenario where malformed macro parameters can lead to improper memory access patterns, resulting in undefined behavior and potential system crashes. The flaw represents a classic example of improper input validation and inadequate boundary checking, which aligns with CWE-129, which addresses issues related to insufficient checking of the length, size, or count of data structures.
From an operational perspective, this vulnerability presents a significant remote denial of service risk to systems that utilize NASM for automated assembly processing or those that accept untrusted assembly code inputs. Attackers can craft malicious macro definitions that exploit the parameter count validation gap, causing the assembler to attempt accessing memory locations outside of allocated bounds. This can result in segmentation faults, application crashes, or complete system instability when the vulnerable NASM instance processes the malicious input. The impact extends beyond simple service disruption as it can affect automated build systems, continuous integration pipelines, and any environment where NASM is used to process potentially untrusted assembly code.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion or system instability. Organizations relying on NASM for assembly processing should consider this vulnerability as a potential vector for service disruption attacks, particularly in environments where assembly code is processed from external sources or where automated assembly operations occur. The remote nature of the vulnerability means that systems processing untrusted assembly input are at risk regardless of network segmentation or firewall configurations.
Mitigation strategies for CVE-2017-17815 primarily involve upgrading to a patched version of NASM where the parameter validation logic has been corrected. Organizations should also implement input validation measures when processing assembly code, particularly in automated environments where untrusted inputs may be encountered. Additionally, deploying network segmentation and access controls to limit exposure of systems running vulnerable NASM versions can help reduce the attack surface. The fix implemented in subsequent releases typically involves adding proper validation checks to ensure that minimum parameter counts do not exceed maximum parameter counts, thereby preventing the illegal address access condition that leads to the denial of service state.