CVE-2026-9499
Out-of-bounds read in QTextCodec::codecForName() in Qt
No known exploitation. EPSS puts it in the 20th percentile. A vendor fix is available.
What to do
The vendor has published a fix. Version details are below where the sources state them.
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Not in the catalog. CISA has not confirmed exploitation.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
0.3% chance of exploitation activity in the next 30 days, which ranks it in the 20th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
10 events over 15 days, from the signal feeds we watch.
- OpenVAS check added
- Patch availablerecord updated
- Patch availablerecord updated
- Patch availablepublished, weakness classified, att&ck mapped, record updated
Affected products
Technical detail
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
Sources
References in the record
- codereview.qt-project.org/c/qt/qt5compat/+/723911
- codereview.qt-project.org/c/qt/qt5compat/+/724348
- codereview.qt-project.org/c/qt/qt5compat/+/724995
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