CVE-2020-11739 Race condition in n/a
A malicious guest OS can exploit missing memory barriers in Xen read-write locks to cause denial of service, leak memory, or potentially escalate privileges.
- 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-2020-11739?
CVE-2020-11739 is a high-severity vulnerability in Debian Debian Linux, published on 14 Apr 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 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded.
Weakness: CWE-362
Which versions are affected by CVE-2020-11739?
It affects 4 products.
Products include Debian Debian Linux, Fedoraproject Fedora, Opensuse Leap, Xen Xen.
How do I fix CVE-2020-11739?
Apply the vendor's patch.
Is CVE-2020-11739 being exploited?
There is no known exploitation of CVE-2020-11739 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2020-11739, DEBIAN-CVE-2020-11739, GHSA-5wwp-3576-jfjc, UBUNTU-CVE-2020-11739.