CVE-2016-5131 in libxml2
Summary
by MITRE
Use-after-free vulnerability in libxml2 through 2.9.4, as used in Google Chrome before 52.0.2743.82, allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to the XPointer range-to function.
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Analysis
by VulDB Data Team • 12/04/2025
The CVE-2016-5131 vulnerability represents a critical use-after-free flaw in the libxml2 library version 2.9.4 and earlier, which was prominently exploited in Google Chrome before version 52.0.2743.82. This vulnerability falls under the Common Weakness Enumeration category CWE-416, which specifically addresses use-after-free conditions where memory is accessed after it has been freed, creating potential for arbitrary code execution or denial of service. The flaw manifests within the XPointer range-to function implementation, a feature designed to handle range expressions in XML documents, making it particularly dangerous in web browser environments where XML processing is common.
The technical exploitation of this vulnerability occurs when maliciously crafted XML content is processed by the affected browser engine, triggering a sequence where memory allocated for XPointer range operations is freed but subsequently accessed during the processing of the range-to function. This memory management error creates a scenario where attackers can manipulate the freed memory location to execute arbitrary code or cause the browser to crash. The vulnerability is particularly concerning because it leverages the XML parsing capabilities that are frequently used in web applications, making it an attractive target for remote exploitation. The XPointer functionality is part of the XML standard for addressing parts of XML documents, and its implementation in libxml2 contained a flaw where the range-to function did not properly validate memory access patterns during processing.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially enable remote code execution in the context of the affected browser process. When exploited, the vulnerability allows attackers to cause unpredictable behavior including browser crashes, memory corruption, and in some cases complete system compromise. The vulnerability affects not only Google Chrome but also any application relying on libxml2 version 2.9.4 or earlier for XML processing, including various web browsers, desktop applications, and server-side systems. The attack vector requires the victim to process malicious XML content, which can occur through various means such as web pages, email attachments, or document files, making it particularly dangerous in user-facing applications.
Mitigation strategies for CVE-2016-5131 primarily involve immediate patching of the libxml2 library to version 2.9.5 or later, where the use-after-free condition has been addressed through proper memory management and validation of freed memory access. Browser vendors and system administrators should prioritize updating Chrome and other affected browsers to versions that include the patched libxml2 library. Additional defensive measures include implementing strict XML content filtering, disabling unnecessary XML processing capabilities in applications, and employing sandboxing techniques to limit the potential impact of successful exploitation attempts. The vulnerability demonstrates the importance of proper memory management practices in security-critical libraries and highlights the necessity of thorough testing of XML processing functions to prevent similar use-after-free conditions. Organizations should also consider implementing network-based intrusion detection systems that can identify and block suspicious XML content that may be attempting to exploit this vulnerability, aligning with ATT&CK framework techniques related to privilege escalation and defense evasion through memory corruption attacks.