CVE-2021-33458 in yasm
Summary
by MITRE • 07/26/2022
An issue was discovered in yasm version 1.3.0. There is a NULL pointer dereference in find_cc() in modules/preprocs/nasm/nasm-pp.c.
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Analysis
by VulDB Data Team • 07/26/2022
The vulnerability identified as CVE-2021-33458 affects the yasm assembler version 1.3.0 and represents a critical NULL pointer dereference flaw within the find_cc() function located in the modules/preprocs/nasm/nasm-pp.c module. This issue emerges during the preprocessing phase of assembly code compilation when the assembler attempts to locate and process conditional compilation directives. The flaw occurs when the function receives unexpected input parameters or encounters malformed preprocessing directives that result in a null pointer being dereferenced during execution. Such a condition can lead to immediate program termination through segmentation fault or access violation exceptions, effectively causing a denial of service condition that impacts legitimate users attempting to compile assembly code using the affected yasm version.
The technical implementation of this vulnerability stems from inadequate input validation and error handling within the conditional compilation processing subsystem of yasm. When the find_cc() function processes preprocessing directives, it fails to properly validate pointer references before dereferencing them, creating an exploitable condition where malicious or malformed input can trigger the NULL pointer dereference. This type of flaw falls under the category of CWE-476 which specifically addresses NULL pointer dereference vulnerabilities in software systems. The vulnerability exists in the context of preprocessor functionality where yasm attempts to parse and process NASM-style preprocessing directives, making it particularly dangerous in environments where assembly code compilation is automated or integrated into build systems.
The operational impact of CVE-2021-33458 extends beyond simple denial of service scenarios as it can be leveraged by attackers to disrupt legitimate compilation processes in development environments, build servers, and automated testing frameworks. When exploited, this vulnerability can cause cascading failures in software development pipelines where yasm is used as a component in the compilation chain. The vulnerability is particularly concerning in continuous integration environments where automated builds may fail repeatedly due to this NULL pointer dereference, leading to significant development delays and potential security implications in systems where assembly code compilation is part of the security infrastructure. Attackers could potentially craft malicious assembly files or preprocessing directives that trigger this condition, causing compilation failures that may mask more serious security issues or prevent legitimate software from being built and deployed.
Mitigation strategies for CVE-2021-33458 should prioritize immediate patching of affected yasm installations to version 1.3.1 or later where the NULL pointer dereference has been resolved through proper input validation and pointer checking mechanisms. System administrators should also implement monitoring for abnormal compilation failures that may indicate exploitation attempts, particularly in build environments where assembly code compilation is frequent. Additional defensive measures include implementing input sanitization for assembly files processed through yasm, utilizing sandboxed compilation environments, and maintaining up-to-date vulnerability assessments of development toolchains. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to denial of service and supply chain compromise, as it can be used to disrupt software development processes and potentially affect the integrity of compiled binaries. Organizations should also consider implementing runtime protections and intrusion detection systems that monitor for abnormal behavior in compilation processes, as these systems may provide early warning of exploitation attempts targeting this specific vulnerability.