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…