Buffer overflow in LibVNCServer - CVE-2019-20839

Vulnerability identifier: #VU29373

CSH Severity: Medium

CVSS v4: 7.5 [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]

CVE-ID: CVE-2019-20839

CWE-ID: CWE-119

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary when processing long socket filename in libvncclient/sockets.c in LibVNCServer. A remote attacker can rick the victim to connect to server using a specially crafted configuration file, trigger buffer overflow and execute arbitrary code on the target system.

LibVNCServer
libvncserver (Alpine package)
libvncserver (Red Hat package)
libvncserver1 (Ubuntu package)
libvncclient1 (Ubuntu package)
libvncserver
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Red Hat CodeReady Linux Builder for x86_64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for ARM 64
Opensuse
Ubuntu
Fedora
SIMATIC ITC2200 PRO
SIMATIC ITC1500
SIMATIC ITC1500 PRO
SIMATIC ITC1900
SIMATIC ITC1900 PRO
SIMATIC ITC2200

Install update from vendor's website.

LibVNCServer - update to 0.9.13
libvncserver (Alpine package) - update to 0.9.13-r0
libvncserver (Red Hat package) - update to 0.9.11-17.el8
SIMATIC ITC2200 PRO - update to
libvncserver1 (Ubuntu package) - addressed in versions 0.9.10+dfsg-3ubuntu0.16.04.5, 0.9.11+dfsg-1ubuntu1.3, 0.9.12+dfsg-9ubuntu0.2
libvncclient1 (Ubuntu package) - addressed in versions 0.9.10+dfsg-3ubuntu0.16.04.5, 0.9.11+dfsg-1ubuntu1.3, 0.9.12+dfsg-9ubuntu0.2
libvncserver - addressed in versions 0.9.13-2.fc31, 0.9.13-2.fc32
SIMATIC ITC1500 - update to 3.2.1.0
SIMATIC ITC1500 PRO - update to 3.2.1.0
SIMATIC ITC1900 - update to 3.2.1.0
SIMATIC ITC1900 PRO - update to 3.2.1.0
SIMATIC ITC2200 - update to 3.2.1.0
SIMATIC ITC2200 PRO - update to 3.2.1.0

• https://github.com/LibVNC/libvncserver/commit/3fd03977c9b35800d73a865f167338cb4d05b0c1
• https://github.com/LibVNC/libvncserver/compare/LibVNCServer-0.9.12...LibVNCServer-0.9.13

• Multiple vulnerabilities in LibVNCServer
• OpenSUSE Linux update for LibVNCServer
• OpenSUSE Linux update for LibVNCServer
• OpenSUSE Linux update for LibVNCServer
• Buffer overflow in libvncserver (Alpine package)
• Red Hat Enterprise Linux 8 update for libvncserver
• Multiple vulnerabilities in Siemens SIMATIC ITC
• Ubuntu update for libvncserver
• Fedora 32 update for libvncserver
• Fedora 31 update for libvncserver