CVE-2015-7498 in libxml2
Summary
by MITRE
Heap-based buffer overflow in the xmlParseXmlDecl function in parser.c in libxml2 before 2.9.3 allows context-dependent attackers to cause a denial of service via unspecified vectors related to extracting errors after an encoding conversion failure.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-7498 represents a critical heap-based buffer overflow within the libxml2 library's xmlParseXmlDecl function located in parser.c. This flaw exists in versions prior to 2.9.3 and demonstrates a significant security weakness that can be exploited by context-dependent attackers to execute denial of service attacks. The vulnerability specifically manifests during error extraction processes that occur following encoding conversion failures, creating a scenario where malicious input can trigger memory corruption. The heap-based nature of this overflow indicates that the vulnerability affects dynamically allocated memory regions, potentially allowing attackers to overwrite adjacent memory structures and disrupt normal program execution. This type of vulnerability falls under the CWE-121 category of heap-based buffer overflow, which is particularly dangerous due to the unpredictable nature of heap memory layout and the potential for arbitrary code execution or system instability.
The technical exploitation of this vulnerability requires careful crafting of XML input that triggers an encoding conversion failure followed by error extraction processes within the xmlParseXmlDecl function. When libxml2 attempts to parse malformed XML documents with specific encoding issues, the library's error handling mechanism becomes compromised, leading to buffer overflow conditions in the heap memory space. The context-dependent nature of this vulnerability means that successful exploitation requires specific conditions to be met, including proper XML structure that causes the library to enter the problematic code path during parsing operations. Attackers can leverage this weakness by providing specially crafted XML documents that force the library into an encoding conversion failure scenario, followed by error extraction that overflows heap buffers. The vulnerability demonstrates a classic memory safety issue where insufficient bounds checking allows data to be written beyond allocated buffer boundaries, potentially corrupting heap metadata or adjacent memory regions.
The operational impact of CVE-2015-7498 extends beyond simple denial of service, as it can severely disrupt applications and systems that rely on libxml2 for XML processing. Systems utilizing vulnerable versions of libxml2 may experience application crashes, service interruptions, or complete system instability when processing malicious XML input. This vulnerability affects a wide range of applications including web servers, XML processing frameworks, and any software components that depend on libxml2 for parsing XML documents. The denial of service impact can be particularly severe in high-traffic environments where a single malicious XML payload can cause cascading failures across multiple service instances. Network infrastructure devices, web applications, and enterprise systems that process external XML data are all at risk, making this vulnerability particularly concerning for organizations operating in regulated environments where system availability is critical. The vulnerability's presence in a widely-used library means that the attack surface is extensive, potentially affecting thousands of applications and systems globally.
Mitigation strategies for CVE-2015-7498 primarily focus on immediate version updates to libxml2 2.9.3 or later, which contain the necessary patches to address the heap buffer overflow issue. Organizations should conduct comprehensive vulnerability assessments to identify all systems and applications utilizing vulnerable versions of libxml2, including both direct dependencies and indirect usage through other libraries or frameworks. Network administrators should implement input validation and sanitization measures to filter potentially malicious XML content before it reaches applications that utilize libxml2 for parsing. The implementation of proper error handling and memory management practices within applications can provide additional defense-in-depth layers, though these measures cannot fully compensate for the underlying library vulnerability. Security teams should also consider implementing intrusion detection systems that can identify and block known attack patterns targeting this specific vulnerability. Regular security updates and patch management procedures should be enforced across all system environments, with particular attention to ensuring that third-party applications and dependencies are updated to use secure versions of libxml2. This vulnerability aligns with ATT&CK technique T1203, which involves the exploitation of software vulnerabilities for privilege escalation or denial of service, and demonstrates the importance of maintaining up-to-date software libraries to prevent exploitation of known memory safety issues.