An issue was found in the private API function qDecodeDataUrl() in QtCore, which is used in QTextDocument and QNetworkReply, and, potentially, in user code.
This has been assigned the CVE id CVE-2025-5455.
Affected versions: All version of Qt up to and including 5.15.18, from 6.0.0 through 6.5.8, from 6.6.0 through 6.8.3 and 6.9.0. It is fixed in Qt 5.15.19, Qt 6.5.9, Qt 6.8.4, Qt 6.9.1.
Impact: If the function was called with malformed data, for example, an URL that contained a "charset" parameter that lacked a value (such as "data:charset,"), and Qt was built with assertions enabled, then it would hit an assertion, resulting in a denial of service.
Vulnerability Score:
CVSS v4.0: 8.4
Solution: Apply the following patch or update to Qt 6.9.1 or 6.8.4 or 6.5.9 or 5.15.19
6.9: https://download.qt.io/official_releases/qt/6.9/CVE-2025-5455-qtbase-6.9.patch or https://codereview.qt-project.org/c/qt/qtbase/+/642434
6.8: https://download.qt.io/official_releases/qt/6.8/CVE-2025-5455-qtbase-6.8.patch or https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/642469
6.5: https://download.qt.io/official_releases/qt/6.5/CVE-2025-5455-qtbase-6.5.patch or https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/642734
5.15: https://download.qt.io/official_releases/qt/5.15/CVE-2025-5455-qtbase-5.15.patch or https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/643952
