CVE-2026-107479 in Qt
Summary
by MITRE • 11/04/2026
An integer truncation vulnerability in the QTextCodec conversion functions of the Qt 5 Core Compatibility APIs module impacts the Qt Framework. An application using the affected functionality could crash.
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Analysis
by VulDB Data Team • 11/04/2026
The identified security issue resides within the QTextCodec conversion routines, which are a critical component of the Qt 5 Core Compatibility APIs module. This vulnerability is classified as an integer truncation error, a specific type of flaw where data is converted from a larger numeric type to a smaller one without proper validation or handling of overflow conditions. In the context of text encoding and decoding operations, such errors typically occur when calculating buffer sizes, string lengths, or memory offsets based on user-supplied input or external data sources. When an integer value exceeds the capacity of its target variable due to truncation, it results in a significantly smaller number than intended by the application logic. This discrepancy fundamentally breaks the assumptions made by subsequent code blocks regarding memory allocation and boundary checks.
From a technical perspective, this flaw allows for potential out-of-bounds reads or writes depending on how the truncated value is utilized during the conversion process. If the system allocates memory based on the original large integer but accesses it using the truncated small integer, it may lead to inefficient resource usage rather than immediate exploitation. However, if the allocation uses the truncated size while subsequent operations assume the larger logical length, or vice versa, it creates a classic buffer overflow scenario. The specific impact noted is an application crash, which indicates that the vulnerability reliably triggers memory corruption or segmentation faults when triggered by malformed input data during text encoding tasks. This behavior aligns with CWE-197 (Numeric Truncation Error) and often serves as a precursor to more severe vulnerabilities such as heap-based buffer overflows described under CWE-120, where control flow can potentially be hijacked if the crash is not immediate but instead allows for arbitrary code execution in less constrained environments.
The operational impact of this vulnerability centers on availability and potential integrity compromise. For end-users, the primary consequence is application instability, characterized by unexpected termination when processing specific text inputs that trigger the truncation path. This denial-of-service effect can be exploited remotely if an attacker can force a victim to process maliciously crafted data through the affected Qt component. Furthermore, because integer truncations often lead to memory corruption, there remains a latent risk of remote code execution or privilege escalation in scenarios where the application runs with elevated permissions or handles sensitive information in memory before being terminated by the operating system's security mechanisms.
Mitigation strategies should focus on both immediate patching and long-term defensive coding practices. Developers must update their Qt frameworks to versions that include patches for this specific integer truncation flaw, ensuring that all dependencies are synchronized with upstream security fixes. In terms of code-level remediation, engineers should implement rigorous input validation before performing any numeric conversions or memory allocations related to text processing. Utilizing safe arithmetic libraries or compiler flags such as -ftrapv can help detect these errors during development rather than in production. Additionally, adopting static analysis tools that specifically target CWE-197 and dynamic testing methods like fuzzing against the QTextCodec APIs will help identify similar truncation issues across the codebase before they reach deployment stages.