CVE-2019-15690: 
Alibaba Cloud Linux (Aliyun Linux) vulnerability analysis and mitigation

LibVNCServer 0.9.12 release and earlier contains a heap buffer overflow vulnerability within the HandleCursorShape() function in libvncclient/cursor.c. The vulnerability allows an attacker to send cursor shapes with specially crafted dimensions, which can result in remote code execution (Kaspersky ICS-CERT, Red Hat Portal).

The vulnerability is an integer overflow that leads to a heap-based buffer overflow in the HandleCursorShape() function. It has been assigned a CVSS v3 base score of 9.8 by Red Hat, with attack vector being Network, attack complexity Low, requiring no privileges or user interaction. The vulnerability is classified under CWE-190 leading to CWE-122 (Integer Overflow or Wraparound leads to Heap-based Buffer Overflow) (Red Hat Portal).

The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability. Successful exploitation could allow an attacker to execute arbitrary code on the affected system. The vulnerability affects the system when a user or application using libvncserver connects to an untrusted server (Red Hat Portal, Kaspersky ICS-CERT).

The primary mitigation is to update LibVNCServer to the commit with hash 54220248886b5001fbbb9fa73c4e1a2cb9413fed or newer. As a workaround, LibVNCServer should not be used to connect to untrusted servers (Red Hat Portal, Kaspersky ICS-CERT).