The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer 0.9.9 and earlier does not properly handle attempts to send a large amount of ClientCutText data, which allows remote attackers to cause a denial of service (memory consumption or daemon crash) via a crafted message that is processed by using a single unchecked malloc.

Affected: Ubuntu:14.04:LTS: libvncserver

Nicolas Ruff discovered that LibVNCServer incorrectly handled memory when being advertised large screen sizes by the server. If a user were tricked into connecting to a malicious server, an attacker could use this issue to cause a denial of service, or possibly execute arbitrary code. (CVE-2014-6051, CVE-2014-6052)

Nicolas Ruff discovered that LibVNCServer incorrectly handled large ClientCutText messages. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service. (CVE-2014-6053)

Nicolas Ruff discovered that LibVNCServer incorrectly handled zero scaling factor values. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service. (CVE-2014-6054)

Nicolas Ruff discovered that LibVNCServer incorrectly handled memory in the file transfer feature. A remote attacker could use this issue to cause a server to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2014-6055)