CVE-2018-15518 in Qt
Summary
by MITRE
QXmlStream in Qt 5.x before 5.11.3 has a double-free or corruption during parsing of a specially crafted illegal XML document.
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Analysis
by VulDB Data Team • 06/22/2023
The vulnerability identified as CVE-2018-15518 affects QXmlStream functionality within Qt 5.x frameworks prior to version 5.11.3, representing a critical memory safety issue that can lead to arbitrary code execution. This flaw exists in the XML parsing component that processes structured data documents, making it particularly dangerous in applications that handle untrusted input. The vulnerability manifests when the system attempts to parse malformed XML content that exploits memory management errors within the Qt library's XML parser implementation. Security researchers have classified this as a double-free or memory corruption issue, indicating that the parser fails to properly manage memory allocation and deallocation sequences during parsing operations.
The technical nature of this vulnerability stems from improper handling of memory resources when encountering malformed XML documents that contain specific patterns or structures designed to trigger the memory management flaw. During parsing operations, the QXmlStream component allocates memory for various internal data structures and processing elements, but fails to correctly validate or handle edge cases in malformed input. This leads to scenarios where memory locations are freed twice or corrupted through improper pointer operations, creating opportunities for attackers to manipulate the program's memory state. The vulnerability operates at the intersection of memory management and input validation, where the parser's failure to properly sanitize or reject malicious input results in exploitable conditions.
The operational impact of this vulnerability extends across numerous applications that utilize Qt frameworks for XML processing, including web applications, desktop software, and server-side systems that handle XML data. Attackers can exploit this weakness by crafting malicious XML documents that trigger the double-free condition during parsing, potentially leading to denial of service, arbitrary code execution, or information disclosure. The vulnerability affects a wide range of software products that rely on Qt's XML processing capabilities, making it particularly concerning for enterprise environments where such applications are prevalent. Systems running affected Qt versions are at risk when processing any untrusted XML input, including user-generated content, configuration files, or data received from external sources.
Mitigation strategies for this vulnerability require immediate patching of affected Qt installations to versions 5.11.3 or later, where the memory management issues have been addressed through proper input validation and memory handling procedures. Organizations should implement comprehensive input validation measures for all XML processing components, ensuring that malformed or suspicious XML content is rejected before reaching the Qt XML parser. Security teams should also consider implementing application-level protections such as XML schema validation, input sanitization, and runtime monitoring to detect and prevent exploitation attempts. The vulnerability aligns with CWE-415, which addresses double free conditions in memory management, and may map to ATT&CK techniques related to memory corruption exploits and privilege escalation through application vulnerabilities. Regular security assessments and dependency updates remain crucial for maintaining system integrity against similar memory safety issues in third-party libraries.