CVE-2012-2871 in iOS
Summary
by MITRE
libxml2 2.9.0-rc1 and earlier, as used in Google Chrome before 21.0.1180.89, does not properly support a cast of an unspecified variable during handling of XSL transforms, which allows remote attackers to cause a denial of service or possibly have unknown other impact via a crafted document, related to the _xmlNs data structure in include/libxml/tree.h.
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Analysis
by VulDB Data Team • 05/25/2021
The vulnerability identified as CVE-2012-2871 represents a critical flaw in libxml2 version 2.9.0-rc1 and earlier implementations, particularly affecting Google Chrome versions prior to 21.0.1180.89. This issue manifests during the processing of XSL transformations where the library fails to properly handle a specific variable cast operation within the _xmlNs data structure. The flaw exists in the include/libxml/tree.h header file, which serves as a fundamental component in XML document handling and namespace management. The vulnerability demonstrates how seemingly minor implementation details in XML processing libraries can create significant security risks when dealing with malformed or crafted input documents.
The technical root cause of this vulnerability lies in improper type casting during XSL transformation processing, specifically involving the _xmlNs data structure that manages XML namespaces. When Chrome processes XSLT transformations through libxml2, it encounters a scenario where an unspecified variable undergoes an incorrect cast operation, leading to potential memory corruption or unexpected behavior. This issue stems from inadequate input validation and error handling within the XML processing pipeline, particularly when dealing with namespace declarations in XSL documents. The vulnerability creates a condition where remote attackers can craft malicious XML documents that trigger this specific casting error, potentially leading to application instability or more severe consequences.
The operational impact of CVE-2012-2871 extends beyond simple denial of service, as the vulnerability could potentially enable arbitrary code execution or information disclosure depending on the specific execution environment and memory layout. Attackers can exploit this weakness by preparing a crafted XML document containing malicious XSLT transformations that, when processed by the vulnerable Chrome browser, cause the application to crash or behave unpredictably. The vulnerability affects web applications that rely on Chrome's XML processing capabilities, particularly those handling untrusted XML content or XSLT transformations from external sources. This makes it particularly dangerous in web environments where users may encounter crafted content through various attack vectors including malicious websites, email attachments, or compromised web services.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and potentially relates to CWE-122 for buffer overflow vulnerabilities. From an ATT&CK perspective, this issue maps to T1203, which covers Exploitation for Client Execution, and T1059, representing Command and Scripting Interpreter. The attack surface is broad given that Chrome's XML processing capabilities are used across numerous web applications and services. Organizations should implement immediate mitigations including updating to Chrome version 21.0.1180.89 or later, which contains the necessary fixes for this vulnerability. Additionally, administrators should consider implementing content filtering mechanisms that can detect and block suspicious XML content, particularly when processing external or untrusted sources. The fix typically involves proper type checking and validation of namespace variables during XSL transformation processing, ensuring that casting operations maintain data integrity and prevent memory corruption scenarios.