CVE-2026-9499: 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 exa

unknownCVE-2026-9499

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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: unknown
Published: 2026-07-21
Last updated: 2026-07-23
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-9499

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-94990.30% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 22% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-9499	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

medium[NEW] [medium] QT: Vulnerability allows denial of servicecert-bund

Recent advisories for An out-of-bounds read

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-67306: FreeRDP versions 3.28.0 and earlier contain an out-of-bounds read vulnerability in the RDP6 pl…nvd · 2026-08-01
highCVE-2026-67301: FreeRDP before 3.29.0 contains out-of-bounds read vulnerabilities in the async update message …nvd · 2026-08-01
highCVE-2026-67291: FreeRDP before 3.29.0 (affected versions <= 3.28.0) contains a heap out-of-bounds read in upda…nvd · 2026-08-01
highCVE-2026-67290: FreeRDP before 3.29.0 contains a heap out-of-bounds read vulnerability in the TSMF FFmpeg deco…nvd · 2026-08-01
lowCVE-2026-66401: FreeRDP before 3.29.0 contains an out-of-bounds heap read vulnerability in the UVC H.264 exten…nvd · 2026-08-01
mediumGHSA-ff84-5f28-78qj: re2: Out-of-bounds heap read in `exec`/`test`/`match` via attacker-influenced `lastIndex`…ghsa · 2026-07-31