The QSslSocket::sslErrors function in Qt before 4.6.5, 4.7.x before 4.7.6, 4.8.x before 4.8.5, when using certain versions of openSSL, uses an "incompatible structure layout" that can read memory from the wrong location, which causes Qt to report an incorrect error when certificate validation fails and might cause users to make unsafe security decisions to accept a certificate.

The XMLHttpRequest object in Qt before 4.8.4 enables http redirection to the file scheme, which allows man-in-the-middle attackers to force the read of arbitrary local files and possibly obtain sensitive information via a file: URL to a QML application.

The QSharedMemory class in Qt 5.0.0, 4.8.x before 4.8.5, 4.7.x before 4.7.6, and other versions including 4.4.0 uses weak permissions (world-readable and world-writable) for shared memory segments, which allows local users to read sensitive information or modify critical program data, as demonstrated by reading a pixmap being sent to an X server.

Heap-based buffer overflow in the Lookup_MarkMarkPos function in the HarfBuzz module (harfbuzz-gpos.c), as used by Qt before 4.7.4 and Pango, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted font file.