Id:
CVE-2020-11739
Comment
:
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.
CVSSv2 Score:
6.9
Access vector:
|
LOCAL
|
Access complexity:
|
MEDIUM
|
Authentication:
|
NONE
|
Confidentiality impact:
|
COMPLETE
|
Integrity impact:
|
COMPLETE
|
Availability impact:
|
COMPLETE
|
CVSSv2 Vector:
AV:L/AC:M/Au:N/C:C/I:C/A:C
CVSSv3 Score:
7.8
Attack vector:
|
LOCAL
|
Attack complexity:
|
HIGH
|
Privileges required:
|
LOW
|
User interaction:
|
NONE
|
Scope:
|
CHANGED
|
Confidentiality impact:
|
HIGH
|
Integrity impact:
|
HIGH
|
Availability impact:
|
HIGH
|
CVSSv3 Vector:
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
References: