CVE-2015-8242 in iOS
Summary
by MITRE
The xmlSAX2TextNode function in SAX2.c in the push interface in the HTML parser in libxml2 before 2.9.3 allows context-dependent attackers to cause a denial of service (stack-based buffer over-read and application crash) or obtain sensitive information via crafted XML data.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2015-8242 represents a critical stack-based buffer over-read flaw within the libxml2 library's HTML parser implementation. This issue specifically affects the xmlSAX2TextNode function located in the SAX2.c file within the push interface of the HTML parser. The vulnerability exists in libxml2 versions prior to 2.9.3 and demonstrates how malformed XML input can be exploited to compromise system stability and potentially expose sensitive data. The flaw manifests when the parser processes crafted XML data that triggers an improper memory access pattern during text node processing, creating conditions where the application attempts to read beyond the bounds of allocated memory buffers. This vulnerability falls under the CWE-121 category of Stack-based Buffer Overflow, which is a well-documented weakness in software security that occurs when data is written beyond the boundaries of a fixed-length buffer allocated on the stack. The attack vector is context-dependent, meaning that successful exploitation requires specific conditions involving the structure and content of the XML data being processed by the vulnerable parser implementation.
The operational impact of this vulnerability extends beyond simple denial of service to include potential information disclosure risks that could expose sensitive system data. When an attacker successfully triggers the buffer over-read condition, the application experiences a crash that results in a denial of service, rendering the affected system or application unavailable to legitimate users. However, the more concerning aspect is that the buffer over-read could potentially allow an attacker to read adjacent memory locations, which might contain sensitive information such as cryptographic keys, user credentials, or system configuration data. The stack-based nature of the vulnerability means that the memory corruption occurs in the program's call stack, potentially affecting critical program state and execution flow. This type of vulnerability is particularly dangerous in web applications and server environments where XML processing is common, as it can be exploited through user input or external data sources without requiring special privileges or complex attack scenarios. The vulnerability's classification under the ATT&CK framework would align with techniques involving memory corruption and privilege escalation, as it can be leveraged to gain unauthorized access to system resources or cause service disruption that impacts availability.
Mitigation strategies for CVE-2015-8242 primarily focus on upgrading to libxml2 version 2.9.3 or later, which contains the necessary patches to address the buffer over-read condition. Organizations should prioritize patch management to ensure all systems utilizing libxml2 are updated to secure versions, as the vulnerability affects widely used software components across multiple platforms and applications. Additionally, implementing input validation and sanitization measures can provide defense-in-depth protection by filtering malformed XML data before it reaches the parser, though this approach does not eliminate the underlying vulnerability. Security monitoring should include detection of unusual application crashes or memory access patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in XML parsers and highlights how seemingly benign input processing can become a vector for serious security incidents. Organizations using libxml2 should also consider implementing application-level restrictions on XML processing, such as limiting document size or complexity, to reduce the attack surface and prevent exploitation through resource exhaustion attacks that could complement the buffer over-read vulnerability. Regular security assessments and code reviews focused on memory safety practices can help identify similar vulnerabilities in other software components that may be susceptible to the same class of memory corruption issues.