CVE-2018-16517 in NASM
Summary
by MITRE
asm/labels.c in Netwide Assembler (NASM) is prone to NULL Pointer Dereference, which allows the attacker to cause a denial of service via a crafted file.
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Analysis
by VulDB Data Team • 06/13/2024
The vulnerability identified as CVE-2018-16517 affects Netwide Assembler version 2.14 and earlier, specifically within the asm/labels.c component of the software. This issue manifests as a NULL pointer dereference that occurs when processing malformed input files, creating a condition where the assembler crashes upon encountering specially crafted assembly code. The vulnerability represents a classic denial of service flaw that can be exploited by attackers who submit maliciously constructed assembly files to systems running vulnerable versions of NASM. The flaw exists in the label processing logic where the software fails to properly validate pointer references during the parsing of assembly directives, leading to an unhandled null pointer access that terminates the application execution.
The technical implementation of this vulnerability stems from insufficient input validation within the label handling subsystem of NASM. When the assembler processes assembly code containing malformed label references or improper directive syntax, the internal pointer management fails to check for null values before dereferencing memory addresses. This type of flaw falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The vulnerability is particularly concerning because it can be triggered through normal file processing operations without requiring special privileges or complex attack vectors, making it easily exploitable in scenarios where NASM is used to process untrusted assembly code from external sources.
From an operational perspective, this vulnerability creates significant risks for systems that rely on NASM for compiling assembly code, particularly in automated build environments, compiler toolchains, or any scenario where assembly files are processed from untrusted sources. The denial of service impact can disrupt development workflows, automated testing pipelines, and continuous integration systems that depend on NASM functionality. Attackers can leverage this vulnerability to cause service disruption by submitting malicious assembly files that will cause NASM to crash, potentially leading to extended downtime for development teams or automated systems. The vulnerability also demonstrates poor defensive programming practices that violate fundamental security principles of input validation and error handling.
Mitigation strategies for CVE-2018-16517 should prioritize immediate patching of affected NASM installations to version 2.15 or later where the vulnerability has been resolved. Organizations should implement input validation measures for any assembly files processed through NASM, including scanning for malformed syntax patterns that could trigger the null pointer dereference. Network segmentation and access controls should be implemented to limit exposure of NASM instances to untrusted inputs, particularly in automated processing environments. Additionally, system administrators should monitor for unusual process termination patterns or denial of service conditions that may indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1499 which covers network denial of service attacks, and organizations should consider implementing intrusion detection systems that can identify patterns consistent with exploitation attempts targeting this specific flaw. Regular security assessments of build environments and compiler toolchains should include verification that all components are updated to secure versions, as this vulnerability represents a preventable issue that could be exploited to disrupt legitimate development operations and compromise system availability.