CVE-2026-103653 in Qt
Summary
by MITRE • 11/03/2026
An out-of-bounds read vulnerability in the Qt CoAP message parsing (QCoapInternalReply::createFromFrame()) of the Qt CoAP module. Processing a malformed CoAP message can cause an application using Qt CoAP to crash (loss of availability) or to continue operating on incorrect data (potential loss of integrity).
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in the Qt CoAP module represents a critical security flaw within the QCoapInternalReply::createFromFrame() function, which is responsible for parsing incoming Constrained Application Protocol messages. This specific component handles the deserialization and validation of network packets received by applications utilizing the Qt framework's networking capabilities. The core technical issue stems from an out-of-bounds read condition that occurs when the parser processes a malformed CoAP message. In this scenario, the application fails to adequately validate the length fields or boundary constraints within the incoming data structure before attempting to access memory locations associated with those fields. This lack of rigorous bounds checking allows an attacker who can inject crafted network traffic to trigger a memory read operation that extends beyond the allocated buffer boundaries. Such behavior is characteristic of CWE-125, which defines out-of-bounds read vulnerabilities where software reads past the end or before the beginning of the intended buffer.
The operational impact of this vulnerability is twofold, affecting both the availability and integrity of systems relying on Qt CoAP for communication with IoT devices or constrained networks. In its most immediate manifestation, processing a specifically crafted malformed packet can cause the application to crash due to an illegal memory access exception. This results in a denial of service condition where legitimate users are unable to interact with the affected system, effectively disrupting critical services that depend on continuous CoAP connectivity. Beyond simple crashes, there is a more severe risk associated with data integrity. If the out-of-bounds read does not immediately terminate the process but instead allows execution to continue, the application may proceed using uninitialized or garbage memory values as part of its internal state. This can lead to unpredictable behavior, logic errors, and potential corruption of sensitive data processed by the application. The ability to influence program flow through incorrect data processing aligns with ATT&CK technique T1498, Network Denial of Service, particularly in scenarios where resource exhaustion or service disruption is achieved via malformed inputs rather than volume-based attacks.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate patching and long-term architectural improvements. The primary remediation step involves updating the Qt CoAP module to a version that includes patches addressing the bounds checking logic in QCoapInternalReply::createFromFrame(). Developers must ensure that all dependencies are kept current, as vendors typically release security updates promptly after such vulnerabilities are disclosed. In addition to patching, implementing network-level defenses can provide an additional layer of protection. Deploying intrusion detection systems or firewalls capable of inspecting CoAP traffic for malformed packets and anomalous payload sizes can help filter out malicious inputs before they reach the vulnerable application logic. Furthermore, adopting secure coding practices that emphasize rigorous input validation is essential. Developers should implement strict length checks on all incoming message fields to ensure that subsequent memory operations remain within allocated boundaries. Utilizing static analysis tools during the development lifecycle can also help identify similar patterns of unsafe memory access early in the software development process, reducing the likelihood of such vulnerabilities being introduced into production environments.