CVE-2016-4738 in tvOS
Summary
by MITRE
libxslt in Apple iOS before 10, OS X before 10.12, tvOS before 10, and watchOS before 3 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted web site.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability identified as CVE-2016-4738 represents a critical memory corruption flaw within the libxslt library component that powers Apple's mobile and desktop operating systems. This issue affects multiple Apple platforms including iOS versions prior to 10.0, macOS versions before 10.12, tvOS versions before 10.0, and watchOS versions before 3.0, creating a widespread attack surface across Apple's ecosystem. The vulnerability stems from insufficient input validation and memory management within the XSLT (Extensible Stylesheet Language Transformations) processing functionality that Apple incorporates into its web rendering and document processing pipelines. Security researchers have classified this as a remote code execution vulnerability due to the potential for attackers to craft malicious web content that triggers the memory corruption when processed by affected systems.
The technical exploitation of this vulnerability occurs through crafted web content that leverages the libxslt library's processing of XSLT transformations. When a user visits a malicious website containing specially crafted XSLT elements, the vulnerable libxslt implementation fails to properly validate memory allocations and buffer boundaries during transformation operations. This leads to memory corruption that can be leveraged by remote attackers to execute arbitrary code with the privileges of the affected application or system process. The flaw operates at the intersection of web rendering and XML processing, where the XSLT engine receives untrusted input from web pages and processes it without adequate bounds checking or memory safety mechanisms. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of how XML processing libraries can become attack vectors when proper input sanitization is absent.
The operational impact of CVE-2016-4738 extends beyond simple remote code execution to encompass potential denial of service conditions that can render affected systems unusable. Attackers can craft malicious web pages that either cause system crashes through memory corruption or maintain persistent control over affected devices through code execution. The vulnerability affects all Apple platforms that utilize the libxslt library for web content processing, making it particularly dangerous as users may encounter malicious content while browsing the web or through email attachments. The attack vector requires no user interaction beyond visiting a malicious website, making it particularly insidious from a security perspective. This vulnerability directly maps to ATT&CK technique T1203, which covers exploitation for execution through web-based attack vectors, and demonstrates how modern web browsers and operating systems can become attack surfaces when third-party libraries contain memory safety issues.
Mitigation strategies for this vulnerability require immediate system updates and patches from Apple to address the underlying libxslt memory corruption issues. Organizations should implement network-level protections such as web filtering solutions that can block known malicious domains and content types that might exploit this vulnerability. Browser security configurations should be hardened to limit XSLT processing capabilities where possible, and users should be educated about the risks of visiting untrusted websites. System administrators should monitor for exploit attempts and maintain updated security information exchanges to identify potential attacks targeting this specific vulnerability. The patching process for this vulnerability requires careful deployment across all affected Apple platforms, as the libxslt library is deeply integrated into core system operations. Additionally, implementing network segmentation and access controls can limit the potential impact of successful exploitation attempts, while regular security assessments should verify that systems remain protected against similar memory corruption vulnerabilities in third-party libraries.