CVE-2016-4448 in tvOS
Summary
by MITRE
Format string vulnerability in libxml2 before 2.9.4 allows attackers to have unspecified impact via format string specifiers in unknown vectors.
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Analysis
by VulDB Data Team • 09/06/2022
The CVE-2016-4448 vulnerability represents a critical format string vulnerability within the libxml2 library version 2.9.3 and earlier, which serves as a fundamental XML parsing component in numerous software systems across the computing landscape. This vulnerability falls under the category of CWE-134, which specifically addresses the use of format strings in a context where user-supplied data is not properly sanitized or validated. The flaw manifests when the library processes malformed XML input containing format string specifiers that are not adequately handled during parsing operations. These specifiers can originate from various attack vectors including network-based XML processing, file parsing, or any input mechanism that feeds data into the vulnerable parsing functions.
The technical implementation of this vulnerability stems from improper handling of format string arguments within the libxml2 parsing routines, particularly in functions that perform string formatting operations. When maliciously crafted XML documents contain format specifiers such as %s, %d, or other printf-style formatting characters, the library's internal string processing functions fail to properly escape or validate these inputs before passing them to underlying formatting functions. This creates an opportunity for attackers to inject malicious format specifiers that can lead to memory corruption, information disclosure, or potentially arbitrary code execution depending on the specific implementation details and system configuration. The vulnerability's impact remains unspecified due to the complex nature of format string exploitation and the various potential attack surfaces within the library's extensive codebase.
The operational impact of CVE-2016-4448 extends far beyond simple denial of service scenarios, as the vulnerability can be leveraged across multiple attack vectors and systems that rely on libxml2 for XML processing. Applications and systems utilizing vulnerable versions of libxml2 include web servers, database systems, content management platforms, and various enterprise software solutions that process XML data from untrusted sources. The vulnerability's exploitation potential aligns with ATT&CK technique T1203, which describes the use of format string vulnerabilities for privilege escalation and code execution. Attackers can potentially craft XML payloads that trigger memory corruption when the library attempts to format error messages or process malformed data, leading to unpredictable behavior that may be exploited to gain unauthorized access or cause system instability. The widespread adoption of libxml2 across different operating systems and software platforms amplifies the potential attack surface significantly.
Mitigation strategies for CVE-2016-4448 primarily focus on immediate remediation through version upgrading to libxml2 2.9.4 or later, which contains the necessary patches to address the format string handling issues. System administrators should conduct comprehensive inventory assessments to identify all systems and applications utilizing vulnerable versions of libxml2, as the library is commonly integrated into numerous software stacks including web servers, database engines, and enterprise applications. Additional defensive measures include implementing strict input validation for XML data, deploying web application firewalls that can detect and block suspicious XML patterns, and configuring applications to limit XML document sizes and complexity to reduce exploitation potential. The vulnerability's classification under CWE-134 emphasizes the need for proper input sanitization and validation practices within software development lifecycle processes, particularly when handling user-supplied data in formatting contexts. Organizations should also consider implementing runtime monitoring and intrusion detection systems to identify potential exploitation attempts targeting this vulnerability, as the indirect nature of the attack vector makes traditional signature-based detection challenging.