CVE-2020-29566 Denial of service in n/a
A malicious stubdomain can trigger a stack overflow in the Xen hypervisor, causing a host-wide denial of service on x86 systems.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-29566?
CVE-2020-29566 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 15 Dec 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
An issue was discovered in Xen through 4.14.x. When they require assistance from the device model, x86 HVM guests must be temporarily de-scheduled. The device model will signal Xen when it has completed its operation, via an event channel, so that the relevant vCPU is rescheduled. If the device model were to signal Xen without having actually completed the operation, the de-schedule / re-schedule cycle would repeat. If, in addition, Xen is resignalled very quickly, the re-schedule may occur before the de-schedule was fully complete, triggering a shortcut. This potentially repeating process uses ordinary recursive function calls, and thus could result in a stack overflow. A malicious or buggy stubdomain serving a HVM guest can cause Xen to crash, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are affected. Arm systems are not affected. Only x86 stubdomains serving HVM guests can exploit the vulnerability.
Weakness: CWE-674
Which versions are affected by CVE-2020-29566?
It affects 3 products.
Products include Debian Debian Linux, Fedoraproject Fedora, Xen Xen.
How do I fix CVE-2020-29566?
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-2020-29566 being exploited?
There is no known exploitation of CVE-2020-29566 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2020-29566, DEBIAN-CVE-2020-29566, GHSA-mr64-xwwr-mx4c, UBUNTU-CVE-2020-29566.