An integer truncation vulnerability in the QTextCodec conversion functions of the Qt 5 Core Compatibility APIs module of the Qt Framework has been discovered and has been assigned the CVE id CVE-2026-107479.
Affected versions: from Qt 5.0.0 to Qt 6.8.8, from Qt 6.9.0 to Qt 6.11.2
Affected status is unknown for versions before Qt 5.0.0.
Impact: Availability. An application using the affected functionality could crash.
CVSS 4.0 Score: 1.7 (Low)
Vector String: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/RE:L/U:Green
Mitigation: Where an application passes very large input data to the QTextCodec conversion functions, process the data in smaller chunks using the overloads that take a ConverterState parameter.
Solution: Apply the following patch or update to Qt 6.8.9, Qt 6.11.3 or Qt 6.12.0 or later.
Patches:
dev: https://codereview.qt-project.org/c/qt/qt5compat/+/763226
Qt 6.11: https://codereview.qt-project.org/c/qt/qt5compat/+/766635 or https://download.qt.io/official_releases/qt/6.11/CVE-2026-107479-qt5compat-6.11.diff
Qt 6.8: https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/766683 or https://download.qt.io/archive/qt/6.8/CVE-2026-107479-qt5compat-6.8.diff
