CVE-2013-4549 in Digia
Summary
by MITRE
QXmlSimpleReader in Qt before 5.2 allows context-dependent attackers to cause a denial of service (memory consumption) via an XML Entity Expansion (XEE) attack.
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Analysis
by VulDB Data Team • 01/18/2022
The vulnerability identified as CVE-2013-4549 affects QXmlSimpleReader in Qt versions prior to 5.2, representing a critical security flaw that enables context-dependent attackers to execute denial of service attacks through XML Entity Expansion techniques. This vulnerability resides within the XML parsing functionality of the Qt framework, which is widely used for developing cross-platform applications. The issue manifests when the parser processes malformed XML documents containing excessive entity expansions, leading to uncontrolled memory consumption that can ultimately crash applications or render systems unusable.
The technical flaw stems from insufficient input validation and resource management within the QXmlSimpleReader component. When processing XML documents, the parser does not adequately limit the number of entity expansions or the depth of nested entities that can be processed. This allows attackers to craft malicious XML payloads containing recursive entity references or extremely large entity expansions that consume excessive memory resources. The vulnerability is classified as a classic XML External Entity (XXE) attack vector, where the attacker exploits the parser's handling of entity references to cause resource exhaustion rather than executing arbitrary code. This behavior aligns with CWE-400, which categorizes unchecked resource consumption as a significant security weakness.
The operational impact of CVE-2013-4549 extends beyond simple denial of service conditions, as it affects any application utilizing Qt's XML parsing capabilities. Systems running vulnerable versions of Qt are at risk of memory exhaustion attacks that can be triggered through various attack vectors including web applications, desktop software, or any system that processes external XML input. The vulnerability is particularly concerning because Qt is used across numerous platforms and applications, making the potential attack surface extensive. Attackers can exploit this weakness by submitting malicious XML documents to applications that process user input, leading to memory consumption that can cause system instability, application crashes, or even complete system hangs depending on the resource constraints of the target environment. The attack requires minimal privileges and can be executed remotely, making it a particularly dangerous vulnerability in networked applications.
Mitigation strategies for CVE-2013-4549 primarily focus on upgrading to Qt version 5.2 or later, where the vulnerability has been addressed through improved entity handling and resource limits. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing Qt components are updated promptly. Additional protective measures include implementing strict XML input validation, limiting entity expansion depth, and configuring parsers with appropriate resource constraints. Security teams should also consider implementing network segmentation and monitoring for unusual memory consumption patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of secure coding practices in XML parsers and highlights the need for proper input sanitization, particularly when dealing with external data sources. Organizations should conduct thorough vulnerability assessments to identify all systems using affected Qt versions and prioritize remediation efforts accordingly. The attack pattern associated with this vulnerability aligns with ATT&CK technique T1499.004, which involves resource exhaustion attacks, emphasizing the need for robust memory management and input validation controls in application security architectures.