#VU3077 Heap-based buffer overflow in LibVNCServer - CVE-2016-9942
Published: January 2, 2017
Vulnerability identifier: #VU3077
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2016-9942
CWE-ID: CWE-119
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
LibVNCServer
LibVNCServer
Software vendor:
LibVNC
LibVNC
Description
The vulnerability allows a remote attacker to execute arbitrary code on vulnerable client system.
A heap-based buffer overflow vulnerability exists due to boundary error in ultra.c in LibVNCClient software, which is bundled with LibVNCServer. A remote attacker can trick the victim to connect to malicious VNC server, send a specially crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions, and trigger buffer overflow.
Successful exploitation of the vulnerability may allow an attacker to execute arbitrary code on vulnerable VNC client.
A heap-based buffer overflow vulnerability exists due to boundary error in ultra.c in LibVNCClient software, which is bundled with LibVNCServer. A remote attacker can trick the victim to connect to malicious VNC server, send a specially crafted FramebufferUpdate message with the Ultra type tile, such that the LZO payload decompressed length exceeds what is specified by the tile dimensions, and trigger buffer overflow.
Successful exploitation of the vulnerability may allow an attacker to execute arbitrary code on vulnerable VNC client.
Remediation
Update to version 0.9.11:
https://github.com/LibVNC/libvncserver/tree/LibVNCServer-0.9.11
https://github.com/LibVNC/libvncserver/tree/LibVNCServer-0.9.11