CVE-2008-3529 in Safari
Summary
by MITRE
Heap-based buffer overflow in the xmlParseAttValueComplex function in parser.c in libxml2 before 2.7.0 allows context-dependent attackers to cause a denial of service (crash) or execute arbitrary code via a long XML entity name.
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Analysis
by VulDB Data Team • 11/30/2024
The vulnerability identified as CVE-2008-3529 represents a critical heap-based buffer overflow within the libxml2 XML parsing library, specifically within the xmlParseAttValueComplex function located in the parser.c file. This flaw exists in versions prior to 2.7.0 and demonstrates the classic characteristics of memory corruption vulnerabilities that can be exploited to compromise system integrity. The vulnerability arises from insufficient input validation when processing XML entity names, creating a scenario where attacker-controlled data can overflow allocated memory buffers on the heap. The context-dependent nature of this vulnerability means that exploitation requires specific conditions to be met, typically involving crafted XML documents that trigger the vulnerable parsing path. This type of vulnerability falls under CWE-121, heap-based buffer overflow, which is a well-documented weakness in software security practices. The ATT&CK framework categorizes this under technique T1203, Exploitation for Client Execution, as it enables attackers to execute arbitrary code on systems processing XML content through vulnerable applications.
The technical implementation of this vulnerability occurs when the xmlParseAttValueComplex function processes XML entity declarations containing excessively long entity names. During parsing operations, the function allocates memory buffers to store entity name data, but fails to properly validate the length of input data against allocated buffer boundaries. When an attacker provides an XML document with an entity name exceeding the allocated buffer size, the excess data overflows into adjacent memory regions, potentially corrupting heap metadata or adjacent variables. This heap corruption can manifest in two primary ways: either causing the application to crash through segmentation faults or access violations, or enabling more sophisticated exploitation techniques where the overflow allows for arbitrary code execution. The heap-based nature of the vulnerability means that the corruption affects the program's dynamic memory allocation structures, making exploitation more challenging but potentially more impactful than stack-based buffer overflows.
The operational impact of CVE-2008-3529 extends beyond simple denial of service scenarios to encompass potential remote code execution capabilities that can compromise entire systems. Applications that rely on libxml2 for XML processing, including web servers, content management systems, and enterprise applications, become vulnerable to attacks that can result in complete system compromise. The vulnerability is particularly dangerous in web-facing applications where XML content can be submitted by untrusted users, creating an attack surface that can be exploited through various vectors including web forms, file uploads, or API endpoints that process XML data. The context-dependent nature of the exploit means that not all XML processing scenarios are equally vulnerable, but the potential for exploitation exists whenever the affected parsing function is invoked with attacker-controlled input. Security researchers have noted that the vulnerability's exploitation often requires careful crafting of the XML payload to ensure proper triggering of the vulnerable code path, making it less straightforward than some other buffer overflow vulnerabilities but still highly concerning.
Mitigation strategies for CVE-2008-3529 focus primarily on immediate remediation through version updates, as libxml2 version 2.7.0 and later contain patches addressing the buffer overflow condition. Organizations should prioritize upgrading their libxml2 installations to versions 2.7.0 or higher, as this represents the most effective defense against exploitation. Additionally, input validation measures can provide defense-in-depth protection, including implementing strict limits on XML entity name lengths and employing XML schema validation to restrict the types of content that can be processed. Network-based mitigations such as web application firewalls can help detect and block suspicious XML content patterns that may attempt to trigger the vulnerability. Security monitoring should include detection of unusual XML processing behavior and memory allocation patterns that could indicate exploitation attempts. The vulnerability underscores the importance of maintaining current security patches and implementing comprehensive application security practices, as demonstrated by the ATT&CK technique T1595, Active Scanning, which involves identifying vulnerable software versions that can be targeted for exploitation. Organizations should also consider implementing sandboxing techniques for XML processing and employing memory corruption detection tools to identify potential exploitation attempts in real-time environments.