A use-after-free vulnerability in the Qt QNetworkAccessManager HTTP/2 client support of the Qt Network module has been discovered and has been assigned the CVE id CVE-2026-95620.
Affected versions: from Qt 6.9.0 to Qt 6.11.2
Impact: A malicious or compromised HTTP/2 server may cause the client application to crash, affecting availability.
CVSS 4.0 Score: 2.1 / Low
Vector String: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/AU:N/R:U/RE:L/U:Green
Mitigation: Disable HTTP/2 for the affected requests using QNetworkRequest::setAttribute(QNetworkRequest::Http2AllowedAttribute, false).
Solution: Apply the following patch or update to Qt 6.11.3 or Qt 6.12.0 or later.
Patches:
dev: https://codereview.qt-project.org/c/qt/qtbase/+/759717
Qt 6.11: https://codereview.qt-project.org/c/qt/qtbase/+/768245 or https://download.qt.io/official_releases/qt/6.11/CVE-2026-95620-qtbase-6.11.diff
Credit: We would like to thank Daniel Birtwhistle for discovering and responsibly reporting this vulnerability, and for his help in verifying the fix.
