CVE-2015-7499 in iOS
Summary
by MITRE
Heap-based buffer overflow in the xmlGROW function in parser.c in libxml2 before 2.9.3 allows context-dependent attackers to obtain sensitive process memory information via unspecified vectors.
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Analysis
by VulDB Data Team • 07/11/2022
The heap-based buffer overflow vulnerability in libxml2's xmlGROW function represents a critical security flaw that emerged in versions prior to 2.9.3, classified under CWE-122 as insufficient validation of length of input. This vulnerability resides within the parser.c file and specifically targets the xmlGROW function which handles memory allocation for XML parsing operations. The flaw enables attackers to manipulate heap memory structures through context-dependent attack vectors, potentially leading to information disclosure and system compromise.
The technical implementation of this vulnerability stems from improper bounds checking during dynamic memory allocation within the XML parser's memory management subsystem. When the xmlGROW function processes incoming XML data, it fails to adequately validate the size parameters used for heap allocation, creating opportunities for attackers to craft malicious XML inputs that trigger buffer overflows. This type of vulnerability operates at the intersection of memory corruption and information disclosure, where the overflow conditions can be leveraged to read sensitive data from adjacent memory locations, potentially exposing process memory contents including stack canaries, return addresses, or other critical system information.
From an operational perspective, this vulnerability poses significant risks to systems relying on libxml2 for XML processing, particularly in web applications, enterprise software, and security tools that parse untrusted XML data. Attackers can exploit this flaw through various vectors including XML external entity (XXE) attacks, malformed XML inputs, or by manipulating XML processing directives. The context-dependent nature of the vulnerability means that successful exploitation requires specific conditions related to the input data structure and processing environment, but once triggered, it can provide attackers with access to sensitive process memory information that could be used for further exploitation or system compromise.
The impact of this vulnerability extends beyond simple information disclosure, as it can serve as a stepping stone for more sophisticated attacks. Security researchers have noted that such heap-based buffer overflows often provide attackers with memory layout information that can be leveraged for bypassing security mechanisms like stack canaries, ASLR, and DEP. The vulnerability's classification aligns with ATT&CK technique T1059.007 for scripting and T1550.002 for use of stolen credentials, as compromised systems may reveal authentication tokens or other sensitive data stored in memory. Organizations using affected versions of libxml2 should implement immediate mitigations including patching to version 2.9.3 or later, input validation, and sandboxing of XML processing operations to prevent exploitation.
Mitigation strategies for this vulnerability should include immediate deployment of the patched libxml2 version 2.9.3 or higher, which addresses the heap overflow conditions through proper bounds checking and memory allocation validation. Additional protective measures include implementing strict XML input validation, employing XML parsers with enhanced security features, and configuring application-level restrictions on XML processing capabilities. Security monitoring should focus on detecting unusual XML processing patterns and memory access anomalies that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in security-critical libraries and reinforces the need for comprehensive security testing including fuzzing and memory corruption analysis to prevent similar flaws in software components that handle structured data processing.