CVE-2017-10686 in Netwide Assembler
Summary
by MITRE
In Netwide Assembler (NASM) 2.14rc0, there are multiple heap use after free vulnerabilities in the tool nasm. The related heap is allocated in the token() function and freed in the detoken() function (called by pp_getline()) - it is used again at multiple positions later that could cause multiple damages. For example, it causes a corrupted double-linked list in detoken(), a double free or corruption in delete_Token(), and an out-of-bounds write in detoken(). It has a high possibility to lead to a remote code execution attack.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability CVE-2017-10686 represents a critical heap memory corruption issue within the Netwide Assembler (NASM) version 2.14rc0, specifically affecting the nasm tool component. This vulnerability stems from improper memory management practices where heap allocated memory is freed in one function but subsequently accessed in multiple locations, creating a classic use-after-free condition that can be exploited by malicious actors. The flaw manifests in the token() function where memory allocation occurs, followed by freeing in the detoken() function which is invoked by pp_getline(), creating a dangerous window where memory pointers remain valid but the underlying memory has been released.
The technical implementation of this vulnerability exposes multiple attack vectors through different memory corruption patterns that can be leveraged by an attacker. The primary issue occurs when memory allocated in token() is freed by detoken() but then accessed again at various positions within the codebase, leading to what is classified as a heap use-after-free condition under CWE-416. The specific corruption patterns include a corrupted double-linked list error within detoken() function, a double free or corruption error in delete_Token(), and an out-of-bounds write condition in detoken() itself. These memory corruption patterns are particularly dangerous because they can be triggered through malformed input processing and provide multiple pathways for exploitation.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable remote code execution attacks, making it a severe security concern for systems that process untrusted assembly code or configuration files through NASM. When exploited successfully, attackers can manipulate the heap memory layout to achieve arbitrary code execution, potentially allowing them to execute malicious payloads with the privileges of the user running the vulnerable nasm tool. This vulnerability affects not only direct usage scenarios but also automated build systems, continuous integration pipelines, and any environment where NASM processes user-supplied assembly code or configuration files that may contain malicious input.
The exploitation of this vulnerability aligns with several ATT&CK tactics including privilege escalation and execution through the use of memory corruption techniques. The vulnerability can be triggered during normal operation when NASM processes malformed input, making it particularly dangerous in environments where the tool processes untrusted or user-provided assembly code. The high probability of remote code execution makes this vulnerability particularly attractive to threat actors, as it can be exploited through various attack vectors including file processing, network-based attacks, or supply chain compromises. Organizations should implement immediate mitigations including updating to patched versions of NASM, implementing input validation controls, and deploying memory protection mechanisms such as address space layout randomization and stack canaries to reduce the exploitability of this and similar heap-based vulnerabilities.