CVE-2017-17812 in NASM
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there is a heap-based buffer over-read in the function detoken() 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-2017-17812 represents a critical heap-based buffer over-read flaw within the Netwide Assembler (NASM) version 2.14rc0. This issue resides in the detoken() function located within the asm/preproc.c source file, fundamentally compromising the integrity of the assembler's preprocessing phase. The flaw manifests when NASM processes malformed input files, specifically those containing crafted assembly directives or tokens that trigger the vulnerable code path. The buffer over-read occurs because the function fails to properly validate the boundaries of memory allocations when processing tokenized input, leading to unauthorized memory access beyond allocated heap regions.
The technical exploitation of this vulnerability enables remote attackers to induce a denial of service condition through carefully constructed input files that, when processed by NASM, trigger the buffer over-read scenario. This occurs during the preprocessing stage where NASM parses and tokenizes assembly source code before compilation, making the attack surface particularly concerning for automated build systems and online code compilation services. The heap-based nature of the vulnerability means that the over-read can potentially expose sensitive memory contents or cause memory corruption that leads to application termination, effectively preventing legitimate assembly operations from completing successfully. According to CWE classification, this vulnerability maps to CWE-125: Out-of-bounds Read, which specifically addresses situations where programs read memory locations beyond the intended buffer boundaries, creating potential for both denial of service and information disclosure scenarios.
The operational impact of CVE-2017-17812 extends beyond simple service disruption, as it can be leveraged in broader attack chains within software development environments. Build servers, continuous integration systems, and online assembly compilers that utilize NASM as part of their processing pipeline become vulnerable to remote exploitation, potentially allowing attackers to disrupt development workflows or gain unauthorized access to build environments. The vulnerability's remote attack potential means that malicious actors can craft assembly files that, when processed by vulnerable NASM versions, will cause system instability or complete application crashes. Organizations relying on NASM for automated assembly processing, particularly those in cybersecurity tool development or embedded systems programming, face significant risk from this flaw. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for "Endpoint Denial of Service" as it specifically targets the availability of endpoint systems through memory corruption attacks, while also potentially enabling information gathering through memory exposure.
Mitigation strategies for CVE-2017-17812 primarily focus on immediate version updates to NASM 2.14rc1 or later, which contain the necessary code fixes to prevent the buffer over-read condition in the detoken() function. System administrators should implement comprehensive patch management procedures to ensure all instances of NASM within development environments are updated to secure versions. Additionally, input validation measures should be implemented at the system level to sanitize assembly source files before processing, particularly in automated environments where untrusted code execution is possible. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to reduce the effectiveness of potential exploitation attempts, though these measures are secondary to the core patching requirement. Regular security audits of build environments and development tools should include checks for vulnerable NASM versions to prevent exploitation through supply chain attacks or compromised development systems.