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CVE-2020-25603

Published: 23 September 2020

An issue was discovered in Xen through 4.14.x. There are missing memory barriers when accessing/allocating an event channel. Event channels control structures can be accessed lockless as long as the port is considered to be valid. Such a sequence is missing an appropriate memory barrier (e.g., smp_*mb()) to prevent both the compiler and CPU from re-ordering access. A malicious guest may be able to cause a hypervisor crash resulting in a Denial of Service (DoS). Information leak and privilege escalation cannot be excluded. Systems running all versions of Xen are affected. Whether a system is vulnerable will depend on the CPU and compiler used to build Xen. For all systems, the presence and the scope of the vulnerability depend on the precise re-ordering performed by the compiler used to build Xen. We have not been able to survey compilers; consequently we cannot say which compiler(s) might produce vulnerable code (with which code generation options). GCC documentation clearly suggests that re-ordering is possible. Arm systems will also be vulnerable if the CPU is able to re-order memory access. Please consult your CPU vendor. x86 systems are only vulnerable if a compiler performs re-ordering.

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

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
(4.11.4+37-g3263f257ca-1)
kinetic Not vulnerable
(4.11.4+37-g3263f257ca-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.