CVE-2026-78253

Incomplete cleanup in Qt Network's Schannel support on Windows can lead to a Denial of Service over time. Affects Qt from 5.15.0 through 6.8.3 and from 6.9.0 before 6.9.2.

QDomDocument XML parsing is vulnerable to a remotely-triggerable denial-of-service crash when processing untrusted input.

An out-of-bounds read vulnerability in QTextCodec::codecForName() in Qt. When called with a non-NUL-terminated QByteArray, the codec-name matching routine reads past the buffer. This usually results in incorrect codec selection; worst case, it causes a crash (DoS). Affects Qt5Compat module from Qt 6.0.0 and Qt Core in Qt 4.x and 5.x.

In Qt Quick, the Text component lacks validation of width and height in the <img> tag, potentially causing excessive resource allocation and application unresponsiveness. Affects Qt from 5.0.0 through 6.10.0.

A vulnerability in Qt's QColorTransferGenericFunction causes a denial of service when passing values outside the expected range, e.g., when processing a specially crafted ICC profile via QColorSpace::fromICCProfile. Affects Qt from 6.6.0 through 6.8.3 and from 6.9.0 through 6.9.1; fixed in 6.8.4 and 6.9.2.

A Use-After-Free vulnerability in Qt's QHttp2ProtocolHandler in the QtNetwork module affects only HTTP/2 handling. It arises from a race condition between uploading POST request body and simultaneous handling of HTTP errors. Affects only Qt 6.9.0; fixed in Qt 6.9.1.

A vulnerability in Qt causes a crash when loading a specially crafted ICNS image file via QImage. Affects Qt versions 6.3.0 through 6.5.9, 6.6.0 through 6.8.4, and 6.9.0. Fixed in 6.5.10, 6.8.5, and 6.9.1.

An issue was found in the private API function qDecodeDataUrl() in QtCore, used in QTextDocument and QNetworkReply. Calling it with malformed data, e.g., a URL with a "charset" parameter lacking a value, triggers an assertion and aborts the program (denial of service).

A symlink attack vulnerability was found in the Qt corelib module on Windows via QFileSystemEngine. The use of GetTempPath API allows manipulation of temporary file paths, potentially leading to unauthorized access and privilege escalation.

A heap-based buffer overflow vulnerability was found in QTextMarkdownImporter in Qt. It occurs when processing a malformed Markdown file. Affects Qt versions 6.8.0 to 6.8.4; versions up to 6.6.0 are unaffected, and the fix is in 6.8.4 and later.