An issue was discovered in the HTTP2 implementation in Qt before 5.15.17, 6.x before 6.2.11, 6.3.x through 6.5.x before 6.5.4, and 6.6.x before 6.6.2. network/access/http2/hpacktable.cpp has an incorrect HPack integer overflow check.

In Qt before 5.15.15, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.2, there can be an application crash in QXmlStreamReader via a crafted XML string that triggers a situation in which a prefix is greater than a length.

An issue was discovered in Qt before 5.15.15, 6.x before 6.2.10, and 6.3.x through 6.5.x before 6.5.3. There are infinite loops in recursive entity expansion.

An issue was discovered in Qt before 5.15.15, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.2. Certificate validation for TLS does not always consider whether the root of a chain is a configured CA certificate.

An issue was discovered in Qt before 5.15.15, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.1. When a SVG file with an image inside it is rendered, a QTextLayout buffer overflow can be triggered.

An issue was discovered in Qt before 5.15.14, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.1. Qt Network incorrectly parses the strict-transport-security (HSTS) header, allowing unencrypted connections to be established, even when explicitly prohibited by the server. This happens if the case used for this header does not exactly match.

An issue was discovered in Qt 5.x before 5.15.14, 6.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.1. QDnsLookup has a buffer over-read via a crafted reply from a DNS server.

In Qt before 5.15.14, 6.0.x through 6.2.x before 6.2.9, and 6.3.x through 6.5.x before 6.5.1, QtSvg QSvgFont m_unitsPerEm initialization is mishandled.

Qt before 6.4.3 allows a denial of service via a crafted string when the SQL ODBC driver plugin is used and the size of SQLTCHAR is 4. The affected versions are 5.x before 5.15.13, 6.x before 6.2.8, and 6.3.x before 6.4.3.