An out-of-bounds write vulnerability in the Qt QTextCodec iconv-based encoding of the Qt 5 Compatibility APIs module (Qt Core in Qt 5 and earlier) has been discovered and has been assigned the CVE id CVE-2026-107590.
Affected versions: from Qt 4.5.0 to Qt 6.8.8, from Qt 6.9.0 to Qt 6.11.2
Impact: Under certain conditions, encoding text with QTextCodec may write outside an internal buffer. This can cause the application to crash and may affect data integrity.
CVSS 4.0 Score: 1.9 / Low
Vector String: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N/E:U/R:U/RE:L/U:Green
Mitigation: None
Solution: Apply the following patch or update to Qt 6.8.9, Qt 6.11.3, Qt 6.12.0 or later.
Patches:
dev: https://codereview.qt-project.org/c/qt/qt5compat/+/762752
Qt 6.11: https://codereview.qt-project.org/c/qt/qt5compat/+/766196 or https://download.qt.io/official_releases/qt/6.11/CVE-2026-107590-qt5compat-6.11.diff
Qt 6.8: https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/766290 or https://download.qt.io/archive/qt/6.8/CVE-2026-107590-qt5compat-6.8.diff
