An out-of-bounds read vulnerability in the Qt NTLM authentication handling of the Qt Network module has been discovered and has been assigned the CVE id CVE-2026-105946. Applications using QNetworkAccessManager or QTcpSocket that authenticate with NTLM, including through a proxy, are affected. Affected versions: from Qt 6.8.0 to Qt 6.8.9, from Qt 6.9.0 to Qt 6.11.1 Affected status unknown before Qt 6.8.0 Impact: A malicious server or proxy that requests NTLM authentication can cause the application to read outside the bounds of an allocated buffer. This may disclose application heap memory contents to the remote party and may cause the application to terminate. CVSS 4.0 Score: 5.3 / Medium Vector String: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:H/SC:N/SI:N/SA:N/E:P Mitigation: No workaround is available. Until the update or patches are applied, users can reduce exposure by allowing NTLM authentication only towards trusted servers and proxies. Solution: Update to Qt 6.11.2, Qt 6.8.10 or Qt 6.12.0 or later, or apply the following patches. Patches: dev: https://codereview.qt-project.org/c/qt/qtbase/+/745457 https://codereview.qt-project.org/c/qt/qtbase/+/744448 https://codereview.qt-project.org/c/qt/qtbase/+/745464 Qt 6.11: https://codereview.qt-project.org/c/qt/qtbase/+/746630 https://codereview.qt-project.org/c/qt/qtbase/+/746626 https://codereview.qt-project.org/c/qt/qtbase/+/746632 or https://download.qt.io/official_releases/qt/6.11/CVE-2026-105946-qtbase-6.11-0001.diff https://download.qt.io/official_releases/qt/6.11/CVE-2026-105946-qtbase-6.11-0002.diff https://download.qt.io/official_releases/qt/6.11/CVE-2026-105946-qtbase-6.11-0003.diff Qt 6.8: https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/775946 https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/775958 https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/775969 or https://download.qt.io/archive/qt/6.8/CVE-2026-105946-qtbase-6.8-0001.diff https://download.qt.io/archive/qt/6.8/CVE-2026-105946-qtbase-6.8-0002.diff https://download.qt.io/archive/qt/6.8/CVE-2026-105946-qtbase-6.8-0003.diff
Tero Pelkonen Qt Group Confidential
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