CVE-2018-12891 Denial of service in n/a
A malicious multi-vCPU PV guest can cause a host-wide Denial of Service by bypassing preemption checks in Xen hypervisor code paths.
- 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-2018-12891?
CVE-2018-12891 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 2 Jul 2018. 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 4.10.x. Certain PV MMU operations may take a long time to process. For that reason Xen explicitly checks for the need to preempt the current vCPU at certain points. A few rarely taken code paths did bypass such checks. By suitably enforcing the conditions through its own page table contents, a malicious guest may cause such bypasses to be used for an unbounded number of iterations. A malicious or buggy PV guest may cause a Denial of Service (DoS) affecting the entire host. Specifically, it may prevent use of a physical CPU for an indeterminate period of time. All Xen versions from 3.4 onwards are vulnerable. Xen versions 3.3 and earlier are vulnerable to an even wider class of attacks, due to them lacking preemption checks altogether in the affected code paths. Only x86 systems are affected. ARM systems are not affected. Only multi-vCPU x86 PV guests can leverage the vulnerability. x86 HVM or PVH guests as well as x86 single-vCPU PV ones cannot leverage the vulnerability.
Which versions are affected by CVE-2018-12891?
It affects 2 products.
Products include Debian Debian Linux, Xen Xen.
How do I fix CVE-2018-12891?
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-2018-12891 being exploited?
There is no known exploitation of CVE-2018-12891 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2018-12891, DEBIAN-CVE-2018-12891, GHSA-7945-69h3-wr87, UBUNTU-CVE-2018-12891.