CVE-2026-107157 in Qt
Summary
by MITRE • 10/26/2026
Out-of-bounds read vulnerability in QCborValue::fromCbor() impacts Qt Framework.
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Analysis
by VulDB Data Team • 10/26/2026
The identified security flaw resides within the Qt Framework's Common Binary Representation (CBOR) parsing module, specifically affecting the QCborValue::fromCbor function. This component is responsible for deserializing binary data encoded in the CBOR format into native C++ objects. The vulnerability manifests as an out-of-bounds read, which occurs when the parser attempts to access memory locations that lie outside the allocated buffer boundaries during the processing of malformed or maliciously crafted input streams. In a typical execution flow, this function reads byte sequences from a provided data source and maps them to corresponding CBOR types such as integers, strings, arrays, or maps. When the input stream contains truncated headers, invalid length indicators, or structurally inconsistent payloads, the internal pointer arithmetic used to navigate the binary structure can calculate an address that exceeds the bounds of the allocated memory region.
From a technical perspective, this flaw is classified under CWE-125, which defines out-of-bounds read vulnerabilities where software reads data past the end, or before the beginning, of the intended buffer. The root cause typically stems from insufficient validation of input length parameters against the actual size of the source buffer prior to dereferencing pointers. In the context of Qt's CBOR implementation, this may involve a failure to properly check if a specified byte count for an array or map exceeds the remaining bytes in the stream before initiating a loop that iterates through those elements. If the parser does not rigorously enforce boundary checks during recursive descent into nested structures, it can trigger a read operation on unmapped memory pages or adjacent heap metadata. This behavior violates fundamental principles of safe memory management and exposes the application to information disclosure risks.
The operational impact of this vulnerability is primarily centered around data leakage and potential denial of service conditions. An out-of-bounds read allows an attacker who controls the input stream to potentially exfiltrate sensitive information stored in adjacent memory locations, such as stack variables, other object instances, or cryptographic keys if they reside nearby in memory. While less severe than a write vulnerability, this can still lead to significant confidentiality breaches depending on what data is present in the application's memory space at runtime. Furthermore, accessing invalid memory addresses often triggers segmentation faults or access violations within the operating system, causing the Qt-based application to crash abruptly. This results in a denial of service for users relying on the affected software, particularly if the vulnerability can be triggered by remote network requests or untrusted file uploads processed automatically by the framework.
Mitigation strategies must focus on both immediate patching and long-term defensive coding practices. The primary remediation is to apply the official security update provided by Qt Company that addresses this specific issue in the QCborValue::fromCbor function, ensuring that all boundary checks are correctly implemented before any memory access occurs. Developers integrating or maintaining applications using older versions of the framework should prioritize upgrading to a patched release as soon as possible. In addition to patching, implementing strict input validation at the application layer is recommended. This includes verifying the integrity and length of incoming CBOR data streams before passing them to the parsing function, utilizing sandboxing techniques to limit the impact if an exploit occurs, and employing static analysis tools configured to detect buffer over-read conditions during the software development lifecycle. Adhering to these measures aligns with industry standards for secure coding and helps maintain the integrity and availability of systems relying on Qt's data serialization capabilities.