CVE-2026-107457 in Qt
Summary
by MITRE • 11/02/2026
A memory corruption vulnerability in the QMqttClient class of the Qt MQTT module. Under certain MQTT 5 connection settings between client and server, QMqttClient may corrupt memory, which can cause the application to crash.
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Analysis
by VulDB Data Team • 11/02/2026
The identified security flaw resides within the QMqttClient implementation of the Qt MQTT library, specifically affecting how the component manages state transitions during the establishment of an MQTT 5 connection. This vulnerability is classified as a memory corruption issue, which typically arises when software improperly handles data buffers or fails to validate input parameters before writing them to allocated memory regions. In this specific context, the defect triggers under particular configurations where the client and server negotiate certain MQTT 5 protocol settings. The interaction between these negotiated parameters appears to lead to an invalid state transition or a buffer handling error that results in overwriting adjacent memory locations or accessing freed memory structures. Such behavior is characteristic of vulnerabilities categorized under CWE-120, which covers Buffer Copy without Checking Size of Input, and potentially CWE-787, indicating Out-of-bounds Write operations depending on the exact mechanism of corruption observed during runtime analysis.
The operational impact of this vulnerability is primarily centered around application stability rather than immediate remote code execution or privilege escalation, although memory corruption vulnerabilities inherently carry a risk profile that extends beyond simple crashes. When an attacker can influence the MQTT 5 connection settings to trigger this specific code path, they can cause the QMqttClient instance to corrupt its internal data structures. This corruption inevitably leads to undefined behavior within the host application, most commonly manifesting as a segmentation fault or general protection fault that results in the abrupt termination of the process. For applications relying on persistent MQTT connections for critical telemetry, control signals, or real-time data synchronization, such crashes can lead to significant service disruptions and loss of connectivity. In environments where high availability is paramount, this denial-of-service capability represents a tangible threat to business continuity and operational reliability.
From an offensive security perspective, while the immediate effect is a crash, memory corruption vulnerabilities are often precursors to more severe exploits if additional conditions align with other weaknesses in the application architecture. Attackers might attempt to leverage heap or stack corruption techniques to manipulate control flow, although this requires precise exploitation of the specific memory layout and mitigation technologies present on the target system. The vulnerability maps to MITRE ATT&CK technique T1499, Endpoint Denial of Service, as it allows an adversary to disrupt service availability by inducing a crash through malformed or specifically crafted MQTT 5 connection parameters. It also relates to T1078, Valid Accounts, if the attacker is required to authenticate before triggering the flaw, highlighting the importance of securing all communication endpoints regardless of authentication status.
Mitigation strategies for this vulnerability should focus on both immediate patching and long-term architectural improvements. The primary remediation step is to update the Qt MQTT module to a version that includes the fix for this memory corruption issue, ensuring that developers are using supported releases with active security maintenance. In addition to updating dependencies, application architects should implement robust input validation mechanisms when handling MQTT 5 connection parameters, ensuring that all negotiated settings fall within expected and safe boundaries before being processed by the client library. Enabling compiler-based protections such as Stack Canaries, Address Sanitizers during development, and Data Execution Prevention in production environments can further reduce the likelihood of successful exploitation or aid in detecting memory corruption events early in the software lifecycle. Regular security testing using fuzzing tools targeted at MQTT protocol implementations is also recommended to identify similar edge cases before they reach production systems.