CVE-2020-25708 Denial of service in libvncserver

High 7.5 Published 27 Nov 2020 Updated 4 Aug 2024

A malicious client can cause a denial of service in libvncserver by triggering a divide by zero error via a crafted message.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2020-25708?

CVE-2020-25708 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 27 Nov 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A divide by zero issue was found to occur in libvncserver-0.9.12. A malicious client could use this flaw to send a specially crafted message that, when processed by the VNC server, would lead to a floating point exception, resulting in a denial of service.

Weakness: CWE-369

Which versions are affected by CVE-2020-25708?

It affects 3 products.

Linux distribution packages (26)

`LibVNCServer` SUSE:Enterprise Storage 5	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:HPE Helion OpenStack 8	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Module for Package Hub 15 SP1	All versions	`0.9.10-4.25.1`
`LibVNCServer` SUSE:Linux Enterprise Module for Package Hub 15 SP2	All versions	`0.9.10-4.25.1`
`LibVNCServer` SUSE:Linux Enterprise Point of Sale 11 SP3	All versions	`0.9.1-160.22.1`
`LibVNCServer` SUSE:Linux Enterprise Server 11 SP4-LTSS	All versions	`0.9.1-160.22.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP2-BCL	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP2-LTSS	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP3-BCL	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP3-LTSS	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP4-LTSS	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server 12 SP5	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server for SAP Applications 12 SP2	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server for SAP Applications 12 SP3	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server for SAP Applications 12 SP4	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Server for SAP Applications 12 SP5	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Software Development Kit 12 SP5	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:Linux Enterprise Workstation Extension 15 SP1	All versions	`0.9.10-4.25.1`
`LibVNCServer` SUSE:Linux Enterprise Workstation Extension 15 SP2	All versions	`0.9.10-4.25.1`
`LibVNCServer` SUSE:OpenStack Cloud 7	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:OpenStack Cloud 8	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:OpenStack Cloud 9	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:OpenStack Cloud Crowbar 8	All versions	`0.9.9-17.34.1`
`LibVNCServer` SUSE:OpenStack Cloud Crowbar 9	All versions	`0.9.9-17.34.1`
`LibVNCServer` openSUSE:Leap 15.1	All versions	`0.9.10-lp151.7.12.1`
`LibVNCServer` openSUSE:Leap 15.2	All versions	`0.9.10-lp152.9.8.1`

Products include Debian Debian Linux, Libvncserver Project Libvncserver, Redhat Enterprise Linux.

How do I fix CVE-2020-25708?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2020-25708 being exploited?

There is no known exploitation of CVE-2020-25708 in the wild and no public exploit code.

All Debian Debian Linux vulnerabilities

Sources

Also known as DEBIAN-CVE-2020-25708, DLA-2451-1, GHSA-3xcq-6vjj-wqx7, MGASA-2020-0439, SUSE-SU-2020:14549-1, SUSE-SU-2020:3515-1 and 5 more.