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CVE-2020-11739

Published: 14 April 2020

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.

Notes

AuthorNote
mdeslaur
hypervisor packages are in universe. For
issues in the hypervisor, add appropriate
tags to each section, ex:
Tags_xen: universe-binary
Priority

Medium

CVSS 3 base score: 7.8

Status

Package Release Status
xen
Launchpad, Ubuntu, Debian
bionic Needed

eoan Ignored
(reached end-of-life)
focal
Released (4.11.3+24-g14b62ab3e5-1ubuntu2.3)
groovy Ignored
(reached end-of-life)
hirsute Ignored
(reached end-of-life)
impish Ignored
(reached end-of-life)
jammy Not vulnerable
(4.15.0-1)
precise Does not exist

trusty Does not exist

upstream Needs triage

xenial Needed

Binaries built from this source package are in Universe and so are supported by the community.