CVE-2018-19869 in Qt
Summary
by MITRE
An issue was discovered in Qt before 5.11.3. A malformed SVG image causes a segmentation fault in qsvghandler.cpp.
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Analysis
by VulDB Data Team • 06/22/2023
The vulnerability identified as CVE-2018-19869 represents a critical memory corruption flaw within the Qt framework's Scalable Vector Graphics handling component. This issue specifically affects Qt versions prior to 5.11.3 and stems from inadequate input validation within the qsvghandler.cpp file. The flaw manifests when processing malformed SVG images, leading to a segmentation fault that can result in application crashes and potential system instability. The vulnerability resides in the SVG image parsing logic where the software fails to properly sanitize or validate malformed input data before attempting to process it, creating a pathway for memory access violations that can be exploited by malicious actors.
The technical implementation of this vulnerability follows a classic buffer overread pattern that aligns with CWE-125, which describes out-of-bounds read conditions. When Qt encounters an SVG file with malformed structures or invalid data sequences, the parsing routine in qsvghandler.cpp attempts to access memory locations beyond the allocated buffer boundaries. This occurs because the code does not adequately validate the structure and content of incoming SVG elements before processing them, particularly when dealing with nested elements, malformed coordinates, or unexpected data types within the SVG specification. The segmentation fault results from the processor attempting to access memory that has not been properly allocated or is protected, causing the application to terminate unexpectedly and potentially exposing underlying system resources.
The operational impact of this vulnerability extends beyond simple application crashes to encompass broader security implications within systems that utilize Qt for graphical user interfaces or document processing. Attackers can exploit this flaw by crafting malicious SVG files that trigger the segmentation fault when opened or rendered by applications built on Qt frameworks. This vulnerability affects numerous applications including web browsers, office suites, design tools, and multimedia applications that rely on Qt's SVG rendering capabilities. The exploitability of this issue is enhanced by the fact that SVG files are commonly encountered in email attachments, web content, and file sharing scenarios, making it a prime target for social engineering attacks. Systems running vulnerable Qt versions are at risk of denial of service attacks that can disrupt normal operations and potentially provide attackers with opportunities for further exploitation.
Mitigation strategies for CVE-2018-19869 primarily focus on immediate version updates to Qt 5.11.3 or later releases where the vulnerability has been patched. Organizations should prioritize updating all affected applications that utilize Qt frameworks, particularly those handling user-provided content or external graphics files. Additionally, implementing defensive measures such as SVG validation at the application level, sandboxing of SVG processing components, and network-level filtering of SVG content can provide additional layers of protection. Security teams should also monitor for potential exploitation attempts through intrusion detection systems that can identify malformed SVG file patterns and anomalous application behavior. The ATT&CK framework categorizes this vulnerability under T1203 - Exploitation for Client Execution and T1059 - Command and Scripting Interpreter, as attackers can leverage this flaw to execute malicious code through compromised applications or to cause denial of service conditions that may facilitate further attacks. Organizations should also consider implementing application whitelisting policies to restrict execution of untrusted SVG content and establish incident response procedures for handling potential exploitation attempts.