[Announce] Security advisory: CVE-2026-100140: Integer overflow vulnerability in XML parsing functionality of Qt5Compat impacts Qt

[List for announcements regarding Qt releases and development]

 An integer overflow vulnerability in the Qt XML parsing (Qt5Compat / QXmlSimpleReader) functionality of Qt has been discovered and has been assigned the CVE id CVE-2026-100140.
Affected versions: from Qt 6.0 to Qt 6.8.9, from Qt 6.9.0 to Qt 6.11.2, Qt 6.12.0

Impact: Processing a specially crafted XML document may trigger an integer overflow in the XML parser. This may lead to incorrect internal memory handling. In the worst case this can result in an application crash (denial of service) or data corruption.

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

Mitigation: Validate or reject unreasonably large XML input before parsing.

Solution: Apply the following patches or update to Qt 6.8.10, Qt 6.11.3, Qt 6.12.1 or later.

Patches:
dev:
https://codereview.qt-project.org/c/qt/qt5compat/+/768900
https://codereview.qt-project.org/c/qt/qt5compat/+/764751
https://codereview.qt-project.org/c/qt/qt5compat/+/768901
https://codereview.qt-project.org/c/qt/qt5compat/+/768902
Qt 6.8:
https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/770943
https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/771955
https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/772655
https://codereview.qt-project.org/c/qt/tqtc-qt5compat/+/770944 or https://download.qt.io/archive/qt/6.8/CVE-2026-100140-qt5compat-6.8.zip

Qt 6.11:
https://codereview.qt-project.org/c/qt/qt5compat/+/770916
https://codereview.qt-project.org/c/qt/qt5compat/+/771924
https://codereview.qt-project.org/c/qt/qt5compat/+/772641
https://codereview.qt-project.org/c/qt/qt5compat/+/770917 or https://download.qt.io/official_releases/qt/6.11/CVE-2026-100140-qt5compat-6.11.zip
Qt 6.12:
https://codereview.qt-project.org/c/qt/qt5compat/+/770852
https://codereview.qt-project.org/c/qt/qt5compat/+/771864
https://codereview.qt-project.org/c/qt/qt5compat/+/771863
https://codereview.qt-project.org/c/qt/qt5compat/+/770851 or https://download.qt.io/official_releases/qt/6.12/CVE-2026-100140-qt5compat-6.12.zip



Mahdi Belila

Qt Group



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Confidential
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