CVE-2018-19870 in Qt
Summary
by MITRE
An issue was discovered in Qt before 5.11.3. A malformed GIF image causes a NULL pointer dereference in QGifHandler resulting in a segmentation fault.
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Analysis
by VulDB Data Team • 06/22/2023
The vulnerability identified as CVE-2018-19870 represents a critical NULL pointer dereference flaw within the Qt framework's GIF image handling component. This issue affects Qt versions prior to 5.11.3 and specifically targets the QGifHandler class responsible for processing gif image files. The flaw manifests when the system encounters a malformed gif image file that contains invalid or corrupted data structures, causing the application to attempt to dereference a null pointer during the image parsing process. This type of vulnerability falls under the category of denial of service conditions where the application crashes due to improper memory management during image processing operations. The vulnerability is particularly concerning because it can be triggered through user-controlled input when applications utilize Qt's image handling capabilities to process untrusted gif files.
The technical root cause of this vulnerability stems from insufficient input validation within the QGifHandler implementation. When processing a malformed gif image, the parsing logic fails to properly validate the image data structure before attempting to access memory locations that may not have been properly initialized. This results in a segmentation fault when the application attempts to dereference a NULL pointer that should have been validated or initialized before use. The flaw demonstrates poor defensive programming practices and highlights the importance of robust input validation mechanisms. From a cybersecurity perspective, this vulnerability can be exploited by attackers who craft malicious gif files designed to trigger the specific parsing path that leads to the NULL pointer dereference. The vulnerability is classified as a CWE-476: NULL Pointer Dereference, which is a well-documented weakness that frequently leads to system instability and potential exploitation scenarios.
The operational impact of CVE-2018-19870 extends beyond simple application crashes, as it can be leveraged to disrupt services in applications that rely on Qt's image processing capabilities. Web applications, desktop software, and mobile applications using Qt frameworks are all at risk when they process untrusted gif image files without proper input sanitization. The vulnerability can be particularly dangerous in environments where applications are exposed to user uploads or external image sources, as attackers can craft malicious gif files to cause service disruption or denial of service conditions. This type of vulnerability is often categorized under the ATT&CK framework's T1499.004 technique, which involves network denial of service attacks through application-level exploitation. The segmentation fault resulting from the NULL pointer dereference can cause applications to crash repeatedly, potentially leading to complete service unavailability and requiring system restarts to restore normal operation.
Mitigation strategies for CVE-2018-19870 primarily focus on upgrading to Qt version 5.11.3 or later where the vulnerability has been patched. Organizations should implement comprehensive input validation measures that sanitize all image file inputs before processing, particularly when dealing with user-uploaded content or external image sources. Security teams should also consider implementing application-level restrictions that limit the types of image files accepted and validate file headers before attempting to parse them through Qt's image handlers. Additionally, deploying intrusion detection systems that can identify attempts to submit malformed image files may provide early warning capabilities. The patch for this vulnerability typically involves enhanced input validation within the QGifHandler class to properly handle malformed gif files and prevent NULL pointer dereference conditions. Organizations should also conduct thorough testing of their applications after applying the patch to ensure that the fix does not introduce any regressions in image processing functionality while maintaining robust protection against this specific denial of service vulnerability.