CVE-2018-20592 in Mini-XML
Summary
by MITRE
In Mini-XML (aka mxml) v2.12, there is a use-after-free in the mxmlAdd function of the mxml-node.c file. Remote attackers could leverage this vulnerability to cause a denial-of-service via a crafted xml file, as demonstrated by mxmldoc.
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Analysis
by VulDB Data Team • 06/22/2023
The vulnerability identified as CVE-2018-20592 represents a critical use-after-free condition within the Mini-XML library version 2.12, specifically affecting the mxmlAdd function located in the mxml-node.c source file. This flaw constitutes a fundamental memory safety issue that arises from improper handling of memory allocation and deallocation sequences during XML document processing. The vulnerability is particularly concerning as it exists within a widely-used lightweight XML parsing library that serves as a foundational component for numerous applications and systems requiring XML data processing capabilities. The flaw manifests when the mxmlAdd function attempts to manipulate memory objects that have already been freed, creating a scenario where subsequent operations may access invalid memory addresses or corrupt memory structures.
The technical exploitation of this vulnerability occurs through the manipulation of XML documents that are processed by the affected Mini-XML library. When a remote attacker crafts a specially designed XML file and feeds it to an application utilizing mxmlAdd functionality, the library's memory management routines fail to properly track object lifecycles, resulting in the reuse of freed memory blocks. This particular use-after-free condition falls under CWE-416, which specifically addresses the use of memory after it has been freed, a category of vulnerabilities that frequently leads to unpredictable behavior and system instability. The vulnerability is particularly dangerous because it can be triggered remotely through XML input processing, making it an attractive target for attackers seeking to disrupt service availability without requiring local system access or elevated privileges.
The operational impact of CVE-2018-20592 extends beyond simple denial-of-service scenarios to potentially enable more sophisticated attacks depending on the application context. When exploited, this vulnerability can cause applications using the affected library to crash or become unresponsive, effectively rendering them unavailable to legitimate users. The demonstration using mxmldoc tool confirms that the issue is not merely theoretical but can be reliably reproduced through proper XML file construction. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves network denial-of-service attacks targeting network infrastructure and application availability. The vulnerability affects any system or application that relies on Mini-XML v2.12 for XML processing, including web applications, embedded systems, and network services that parse XML content, making it a widespread concern across multiple operational domains.
Mitigation strategies for this vulnerability require immediate attention from system administrators and developers who utilize the affected Mini-XML library. The most effective approach involves upgrading to a patched version of the Mini-XML library where the memory management issues in the mxmlAdd function have been resolved through proper object lifecycle handling and memory tracking mechanisms. Organizations should conduct comprehensive inventory assessments to identify all systems and applications that depend on Mini-XML v2.12 and prioritize remediation efforts accordingly. Additionally, implementing input validation measures and XML schema validation can provide additional layers of protection by sanitizing XML content before processing, though these measures do not address the root cause. Security monitoring should be enhanced to detect unusual application behavior or crashes that may indicate exploitation attempts, while network-based intrusion detection systems can be configured to flag suspicious XML content patterns that may be indicative of attempted exploitation. The vulnerability also underscores the importance of regular security updates and dependency management practices within software development lifecycle processes.