CVE-2018-20005 in Mini-XML
Summary
by MITRE
An issue has been found in Mini-XML (aka mxml) 2.12. It is a use-after-free in mxmlWalkNext in mxml-search.c, as demonstrated by mxmldoc.
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Analysis
by VulDB Data Team • 06/13/2023
The vulnerability identified as CVE-2018-20005 represents a critical use-after-free flaw within the Mini-XML library version 2.12, specifically affecting the mxmlWalkNext function in the mxml-search.c source file. This issue manifests when the mxmldoc utility processes malformed XML documents, creating a scenario where freed memory regions are subsequently accessed, potentially leading to arbitrary code execution or application crashes. The vulnerability stems from inadequate memory management practices within the XML traversal logic, where the function fails to properly handle reference counting or memory deallocation sequences during recursive document navigation. Such flaws are particularly dangerous in XML processing libraries since they can be exploited through carefully crafted input files that trigger the problematic code path, making them attractive targets for attackers seeking to compromise systems that utilize Mini-XML for XML document parsing and manipulation.
The technical implementation of this vulnerability aligns with CWE-416, which describes the use of freed memory condition, and demonstrates characteristics consistent with heap-based buffer overflows that can be exploited through memory corruption techniques. The mxmlWalkNext function operates by traversing XML document trees and maintaining internal state information about node positions and traversal contexts. When the function encounters certain malformed XML structures, it may prematurely free memory structures while still maintaining references to them, creating a window where subsequent operations attempt to access already deallocated memory regions. This particular flaw is especially concerning because it affects the core search and traversal functionality of the library, meaning any application that relies on Mini-XML for XML navigation and querying is potentially vulnerable to exploitation.
The operational impact of CVE-2018-20005 extends beyond simple application instability, as it can enable remote code execution in scenarios where vulnerable applications process untrusted XML input. Attackers can craft malicious XML documents that, when processed by applications using the affected Mini-XML library, trigger the use-after-free condition and potentially allow for arbitrary code execution with the privileges of the affected process. This vulnerability affects a wide range of applications that depend on Mini-XML for XML processing, including web applications, document processors, and system tools that parse XML configuration files or data feeds. The exploitation requires minimal privileges and can be automated through web-based interfaces, making it particularly dangerous in environments where XML processing is common and input validation may be insufficient.
Mitigation strategies for CVE-2018-20005 primarily involve upgrading to Mini-XML version 2.13 or later, which includes proper memory management fixes that prevent the use-after-free condition. Organizations should conduct comprehensive vulnerability assessments to identify all applications and systems that utilize Mini-XML, particularly those that process external XML input. Additionally, implementing strict input validation measures, sandboxing XML processing operations, and employing automated security scanning tools can help reduce the attack surface. The vulnerability also highlights the importance of following secure coding practices such as those outlined in the OWASP Secure Coding Practices and the CERT Secure Coding Standards, which emphasize proper memory management and the prevention of use-after-free conditions through careful reference counting and memory lifecycle management. System administrators should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, while maintaining regular patching schedules to address similar vulnerabilities in the broader software ecosystem.