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Ubuntu: USN-5617-1 (CVE-2020-11739): Xen vulnerabilities

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Ubuntu: USN-5617-1 (CVE-2020-11739): Xen vulnerabilities

Severity
7
CVSS
(AV:L/AC:M/Au:N/C:C/I:C/A:C)
Published
04/14/2020
Created
09/21/2022
Added
09/20/2022
Modified
09/20/2022

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.

Solution(s)

  • ubuntu-upgrade-libxendevicemodel1
  • ubuntu-upgrade-libxenevtchn1
  • ubuntu-upgrade-libxengnttab1
  • ubuntu-upgrade-libxenmisc4-11
  • ubuntu-upgrade-xen-hypervisor-4-11-amd64
  • ubuntu-upgrade-xen-hypervisor-4-11-arm64
  • ubuntu-upgrade-xen-hypervisor-4-11-armhf
  • ubuntu-upgrade-xen-utils-4-11
  • ubuntu-upgrade-xen-utils-common
  • ubuntu-upgrade-xenstore-utils

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