Out-of-bounds read in UltraVNC - CVE-2019-8261

Vulnerability identifier: #VU22963

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2019-8261

CWE-ID: CWE-125

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to gain access to sensitive information on the target system.

The vulnerability exists due to a boundary condition in VNC code inside client CoRRE decoder, caused by multiplication overflow. A remote attacker that controls a malicious VNC server can trick a user to connect to it, trigger out-of-bounds read error and read contents of memory on the system.

UltraVNC
SIMATIC WinCC Runtime Advanced
SIMATIC HMI KTP900F
SIMATIC HMI KTP900
SIMATIC HMI KTP700F
SIMATIC HMI KTP700
SIMATIC HMI KTP400F
SIMATIC HMI Comfort Panels 4”-22”
SIMATIC HMI Comfort Outdoor Panels 7” & 15”

Install updates from vendor's website.

UltraVNC - update to 1.2.2.3
SIMATIC WinCC Runtime Advanced - update to 16 Update 4
SIMATIC HMI KTP900F - update to 16 Update 4
SIMATIC HMI KTP900 - update to 16 Update 4
SIMATIC HMI KTP700F - update to 16 Update 4
SIMATIC HMI KTP700 - update to 16 Update 4
SIMATIC HMI KTP400F - update to 16 Update 4
SIMATIC HMI Comfort Panels 4”-22” - update to 16 Update 4
SIMATIC HMI Comfort Outdoor Panels 7” & 15” - update to 16 Update 4

• https://ics-cert.kaspersky.com/advisories/klcert-advisories/2019/03/01/klcert-19-007-ultravnc-out-of-bound-read/

• Multiple vulnerabilities in UltraVNC
• Multiple vulnerabilities in Siemens SIMATIC UltraVNC HMI WinCC Products