CVE-2017-17819 in NASM
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there is an illegal address access in the function find_cc() in asm/preproc.c that will cause a remote denial of service attack, because pointers associated with skip_white_ calls are not validated.
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Analysis
by VulDB Data Team • 01/18/2023
The vulnerability identified as CVE-2017-17819 resides within the Netwide Assembler (NASM) version 2.14rc0, a widely used assembler for x86 and x86-64 architectures. This issue manifests as an illegal address access condition within the find_cc() function located in the asm/preproc.c source file, representing a critical flaw that can be exploited remotely to cause system disruption. The vulnerability stems from inadequate validation of pointers that are associated with skip_white_ function calls, creating a scenario where malicious input can trigger unexpected behavior in the assembler's preprocessing phase.
The technical implementation of this vulnerability involves the improper handling of memory pointers during the preprocessing stage of assembly code compilation. When NASM processes input files, the find_cc() function attempts to traverse through whitespace characters using skip_white_ calls without first validating whether the pointers being referenced are properly initialized or within valid memory boundaries. This pointer validation failure creates an exploitable condition where an attacker can craft malicious input that causes the assembler to access invalid memory locations, leading to program termination and denial of service.
From an operational perspective, this vulnerability presents a significant risk to systems that rely on NASM for code compilation, particularly in automated build environments, continuous integration pipelines, or any scenario where external input is processed through the assembler. The remote denial of service attack vector means that adversaries can potentially disrupt legitimate compilation processes without requiring local system access, making this particularly dangerous in networked environments. The impact extends beyond simple service disruption as it can affect entire development workflows and deployment processes that depend on reliable assembly compilation.
The vulnerability aligns with CWE-476, which addresses NULL pointer dereference conditions, and represents a classic example of improper input validation in software preprocessing components. From an attacker's perspective, this flaw maps to ATT&CK technique T1059.001, which involves the use of command-line interfaces, as the assembler's preprocessing phase can be targeted through crafted input files. The remote exploitation capability makes this vulnerability particularly concerning for environments where NASM is used in automated processing systems or web-based compilation services.
Mitigation strategies should focus on immediate patching of affected NASM versions to address the pointer validation issue in the find_cc() function. System administrators should implement input sanitization measures for any files processed through NASM, particularly when dealing with untrusted input sources. Additionally, deploying network segmentation and access controls around systems running NASM can help limit the potential impact of exploitation attempts. Organizations should also consider implementing automated monitoring for abnormal termination patterns in assembly compilation processes as an early detection mechanism for potential exploitation attempts.