It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames. A malicious attacker could exploit this by sending specially crafted WebSocket frames to a server, causing a heap-based buffer overflow.

Affected: Ubuntu:16.04:LTS: libvncserver, Ubuntu:18.04:LTS: libvncserver, Ubuntu:20.04:LTS: libvncserver

It was discovered that LibVNCServer incorrectly handled decompressing data. An attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. (CVE-2019-15680)

It was discovered that an information disclosure vulnerability existed in LibVNCServer when sending a ServerCutText message. An attacker could possibly use this issue to expose sensitive information. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15681)

It was discovered that LibVNCServer incorrectly handled cursor shape updates. If a user were tricked in to connecting to a malicious server, an attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2019-15690, CVE-2019-20788)

It was discovered that LibVNCServer incorrectly handled decoding WebSocket frames. An attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 19.10, Ubuntu 18.04 LTS, and Ubuntu 16.04 LTS. (CVE-2017-18922)