CVE-2016-4571 in mxml
Summary
by MITRE
The mxml_write_node function in mxml-file.c in mxml 2.9, 2.7, and possibly earlier allows remote attackers to cause a denial of service (stack consumption) via crafted xml file.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-4571 affects the mxml library version 2.9, 2.7, and potentially earlier releases, specifically targeting the mxml_write_node function within the mxml-file.c source file. This flaw represents a classic stack-based buffer overflow condition that can be exploited remotely to consume excessive stack memory resources, ultimately leading to a denial of service scenario. The mxml library serves as a lightweight XML parsing and generation library commonly used in embedded systems and applications requiring minimal memory footprint. The vulnerability stems from inadequate input validation and stack memory management within the XML node writing functionality, where recursive processing of malformed XML structures can lead to uncontrolled stack growth.
The technical implementation of this vulnerability involves the manipulation of XML document structures that trigger recursive calls within the mxml_write_node function. When processing specially crafted XML files containing deeply nested elements or circular references, the function executes without proper stack depth limits, causing the call stack to consume excessive memory resources. This behavior aligns with CWE-770, which addresses the allocation of resources without proper limits, and specifically manifests as a stack exhaustion attack pattern. The flaw demonstrates characteristics consistent with the ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect any application utilizing the affected mxml library versions in its XML processing workflows. Systems running embedded applications, IoT devices, or any software that relies on mxml for configuration file handling or data exchange become vulnerable to this attack vector. The vulnerability is particularly concerning in environments where XML processing is frequent or where applications process untrusted XML input from external sources. Attackers can craft malicious XML documents that, when processed by vulnerable applications, trigger the stack consumption behavior and effectively crash the target system or make it unresponsive.
Mitigation strategies for CVE-2016-4571 require immediate attention through library version updates to mxml 2.10 or later, which contain fixes for the stack consumption issue. Organizations should implement input validation measures to sanitize XML data before processing and consider implementing stack limit checks within their XML processing pipelines. Additionally, network segmentation and access controls can help limit exposure by restricting access to XML processing endpoints. The fix implemented in newer mxml versions typically involves introducing proper recursion depth limits and stack memory management to prevent unbounded stack growth during XML node processing operations. Security monitoring should include detection of unusual memory consumption patterns and stack usage metrics to identify potential exploitation attempts.