CVE-2014-0191 in Fusion Middleware
Summary
by MITRE
The xmlParserHandlePEReference function in parser.c in libxml2 before 2.9.2, as used in Web Listener in Oracle HTTP Server in Oracle Fusion Middleware 11.1.1.7.0, 12.1.2.0, and 12.1.3.0 and other products, loads external parameter entities regardless of whether entity substitution or validation is enabled, which allows remote attackers to cause a denial of service (resource consumption) via a crafted XML document.
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Analysis
by VulDB Data Team • 06/22/2022
The vulnerability identified as CVE-2014-0191 represents a critical flaw in the libxml2 XML parser library that affects multiple Oracle products including Oracle Fusion Middleware. This issue stems from improper handling of external parameter entities within the xmlParserHandlePEReference function located in parser.c. The vulnerability exists in libxml2 versions prior to 2.9.2 and specifically impacts Oracle HTTP Server's Web Listener component in Oracle Fusion Middleware versions 11.1.1.7.0, 12.1.2.0, and 12.1.3.0. The flaw allows malicious actors to exploit the parser's behavior by crafting XML documents that trigger excessive resource consumption through uncontrolled loading of external parameter entities.
The technical root cause of this vulnerability lies in the parser's failure to respect entity substitution and validation settings when processing external parameter entities. Normally, XML parsers should respect configuration parameters that control whether external entities are resolved or whether entity substitution occurs. However, in affected versions of libxml2, the parser unconditionally loads external parameter entities regardless of these security settings, creating a path for resource exhaustion attacks. This behavior violates the principle of least privilege and fails to implement proper input validation and sanitization mechanisms that should prevent malicious entity resolution.
The operational impact of this vulnerability manifests as a denial of service condition that can severely impact system availability and performance. Attackers can craft specially designed XML documents that contain references to external parameter entities, causing the affected systems to consume excessive memory and processing resources as they attempt to resolve these entities. The resource consumption can escalate rapidly, potentially leading to complete system unresponsiveness or crash conditions. This vulnerability particularly affects web applications and services that process untrusted XML input, making it a significant concern for enterprise environments where Oracle Fusion Middleware components are deployed. The impact extends beyond individual systems to potentially disrupt business operations and service availability across entire application stacks.
Mitigation strategies for CVE-2014-0191 should focus on immediate patching of affected libxml2 versions to 2.9.2 or later, which contains the necessary fixes to properly respect entity substitution and validation settings. Organizations should also implement XML input validation and sanitization measures at application boundaries to prevent malformed XML from reaching the parser. Network-level controls such as XML firewalls or API gateways can provide additional protection by filtering suspicious XML content before it reaches vulnerable components. Security configurations should be reviewed to ensure that entity resolution is disabled or restricted in environments where untrusted XML input is processed. This vulnerability aligns with CWE-400, which addresses improper handling of resource consumption, and maps to ATT&CK technique T1499.004 for denial of service attacks. System administrators should also monitor for unusual resource consumption patterns and implement automated alerting mechanisms to detect potential exploitation attempts.