Division by zero in LibVNCServer - CVE-2020-25708

Vulnerability identifier: #VU48699

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2020-25708

CWE-ID: CWE-369

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to divide by zero error when processed by the VNC server, would lead to a floating point exception, resulting in a denial of service. A remote attacker can pass specially crafted file to the application and crash it.

LibVNCServer
libvncserver (Red Hat package)
libvncserver (Alpine package)
libvncclient1 (Ubuntu package)
libvncserver1 (Ubuntu package)
vino (Ubuntu package)
Red Hat CodeReady Linux Builder for ARM 64
Red Hat CodeReady Linux Builder for Power, little endian
Red Hat CodeReady Linux Builder for x86_64
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Ubuntu

Install update from vendor's website.

LibVNCServer - update to 0.9.13
libvncserver (Red Hat package) - update to 0.9.11-17.el8
libvncclient1 (Ubuntu package) - addressed in versions 0.9.10+dfsg-3ubuntu0.16.04.6, 0.9.11+dfsg-1ubuntu1.4, 0.9.12+dfsg-9ubuntu0.3
libvncserver1 (Ubuntu package) - addressed in versions 0.9.10+dfsg-3ubuntu0.16.04.6, 0.9.11+dfsg-1ubuntu1.4, 0.9.12+dfsg-9ubuntu0.3
vino (Ubuntu package) - addressed in versions 3.8.1-0ubuntu9.4, 3.22.0-3ubuntu1.2, 3.22.0-5ubuntu2.2, 3.22.0-6ubuntu2.1

• https://bugzilla.redhat.com/show_bug.cgi?id=1896739
• https://github.com/LibVNC/libvncserver/issues/409
• https://github.com/LibVNC/libvncserver/commit/673c07a75ed844d74676f3ccdcfdc706a7052dba

• Division by zero in LibVNC LibVNCServer
• Division by zero in libvncserver (Alpine package)
• Red Hat Enterprise Linux 8 update for libvncserver
• Ubuntu update for libvncserver