An out-of-bounds read vulnerability in the JSON document parsing functionality (QJsonDocument) of the Qt Core module and the Qt 5 Core Compatibility APIs module (QBinaryJson) has been discovered and has been assigned the CVE id CVE-2026-101201.
Affected versions: From Qt 5.0 to Qt 6.8.8, and from Qt 6.9.0 to Qt 6.11.2
Impact: Availability (crash due to out-of-bounds read when processing specially crafted JSON document data)
CVSS 4.0 Score: 4.3 (Medium)
Vector String: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/R:U/RE:L/U:Amber
Mitigation: None available.
Solution: Apply the following patches or update to Qt 6.8.9, Qt 6.11.3, or later.
Patches:
dev: https://codereview.qt-project.org/c/qt/qt5compat/+/758925 and https://codereview.qt-project.org/c/qt%2Fqt5compat/+/759230
Qt 6.11: https://codereview.qt-project.org/c/qt%2Fqt5compat/+/761606 and https://codereview.qt-project.org/c/qt%2Fqt5compat/+/761608
or https://download.qt.io/official_releases/qt/6.11/CVE-2026-101201-qtqt5compat-6.11-0001.diff and https://download.qt.io/official_releases/qt/6.11/CVE-2026-101201-qtqt5compat-6.11-0002.diff
Qt 6.8: https://codereview.qt-project.org/c/qt%2Ftqtc-qt5compat/+/761630 and https://codereview.qt-project.org/c/qt%2Ftqtc-qt5compat/+/761632 or https://download.qt.io/archive/qt/6.8/CVE-2026-101201-qtqt5compat-6.8-0001.diff and https://download.qt.io/archive/qt/6.8/CVE-2026-101201-qtqt5compat-6.8-0002.diff
