#VU31973 Buffer overflow in Xen - CVE-2020-11739

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Main Vulnerability Database Vulnerabilities #VU31973

#VU31973 Buffer overflow in Xen - CVE-2020-11739

Published: July 28, 2020


Vulnerability identifier: #VU31973
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:U/U:Green
CVE-ID: CVE-2020-11739
CWE-ID: CWE-119
Exploitation vector: Adjecent network
Exploit availability: No public exploit available
Vulnerable software:
Xen
Software vendor:
Xen Project

Description

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

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).

Remediation

Install updates from vendor's website.

External links