CVE-2026-9499

Name	CVE-2026-9499
Description	An out-of-bounds read (buffer over-read) vulnerability exists in QTextCodec::codecForName() in Qt. When the function is called with a QByteArray that is not NUL-terminated (for example, one created with QByteArray::fromRawData()), the codec-name matching routine reads past the end of the supplied buffer. In most cases this results in an incorrect text codec being selected; in the worst case, if the over-read reaches unmapped memory, the process crashes (denial of service). The over-read is bounded by the length of the longest codec-name candidate, and the out-of-bounds bytes are only compared internally against Qt's fixed list of codec names, so no data is disclosed to an attacker. Applications that do not pass non-NUL-terminated QByteArrays to QTextCodec::codecForName() are not exposed. The affected code resides in the Qt5Compat module from Qt 6.0.0 onward, and in Qt Core (qtbase) in Qt 4.x and Qt 5.x.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
qt6-5compat (PTS)	bookworm	6.4.2-1	vulnerable
	trixie	6.8.2-3	vulnerable
	forky, sid	6.10.2-3	vulnerable
qtbase-opensource-src (PTS)	bullseye	5.15.2+dfsg-9+deb11u1	vulnerable
	bullseye (security)	5.15.2+dfsg-9+deb11u2	vulnerable
	bookworm	5.15.8+dfsg-11+deb12u3	vulnerable
	trixie	5.15.15+dfsg-6+deb13u1	vulnerable
	forky, sid	5.15.19+dfsg-3	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
qt6-5compat	source	(unstable)	(unfixed)
qtbase-opensource-src	source	(unstable)	(unfixed)

Notes

https://codereview.qt-project.org/c/qt/qt5compat/+/723911
https://codereview.qt-project.org/c/qt/qt5compat/+/724348 (6.11 branch)
https://codereview.qt-project.org/c/qt/qt5compat/+/724995 (6.10 branch)