CVE-2020-25598

MEDIUM
New! CVE Severity Now Using CVSS v3

The calculated severity for CVEs has been updated to use CVSS v3 by default. CVEs that do not have a CVSS v3 score will fall back CVSS v2 for calculating severity. Severity display preferences can be toggled in the settings dropdown.

Description

An issue was discovered in Xen 4.14.x. There is a missing unlock in the XENMEM_acquire_resource error path. The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar to forgetting to unlock a spinlock. A buggy or malicious HVM stubdomain can cause an RCU reference to be leaked. This causes subsequent administration operations, (e.g., CPU offline) to livelock, resulting in a host Denial of Service. The buggy codepath has been present since Xen 4.12. Xen 4.14 and later are vulnerable to the DoS. The side effects are believed to be benign on Xen 4.12 and 4.13, but patches are provided nevertheless. The vulnerability can generally only be exploited by x86 HVM VMs, as these are generally the only type of VM that have a Qemu stubdomain. x86 PV and PVH domains, as well as ARM VMs, typically don't use a stubdomain. Only VMs using HVM stubdomains can exploit the vulnerability. VMs using PV stubdomains, or with emulators running in dom0, cannot exploit the vulnerability.

References

http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00008.html

https://lists.fedoraproject.org/archives/list/[email protected]/message/4JRXMKEMQRQYWYEPHVBIWUEAVQ3LU4FN/

https://lists.fedoraproject.org/archives/list/[email protected]/message/DA633Y3G5KX7MKRN4PFEGM3IVTJMBEOM/

https://lists.fedoraproject.org/archives/list/[email protected]/message/RJZERRBJN6E6STDCHT4JHP4MI6TKBCJE/

https://security.gentoo.org/glsa/202011-06

https://xenbits.xen.org/xsa/advisory-334.html

Details

Source: MITRE

Published: 2020-09-23

Updated: 2020-11-11

Type: CWE-670

Risk Information

CVSS v2

Base Score: 2.1

Vector: AV:L/AC:L/Au:N/C:N/I:N/A:P

Impact Score: 2.9

Exploitability Score: 3.9

Severity: LOW

CVSS v3

Base Score: 5.5

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Impact Score: 3.6

Exploitability Score: 1.8

Severity: MEDIUM

Tenable Plugins

View all (10 total)

IDNameProductFamilySeverity
144794XENMEM_aquire_resources Error Path DoS (XSA-334)NessusMisc.
medium
143853SUSE SLES12 Security Update : xen (SUSE-SU-2020:2788-1)NessusSuSE Local Security Checks
medium
143707SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:2791-1)NessusSuSE Local Security Checks
medium
143685SUSE SLES12 Security Update : xen (SUSE-SU-2020:2786-1)NessusSuSE Local Security Checks
medium
143637SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2020:2790-1)NessusSuSE Local Security Checks
medium
142854GLSA-202011-06 : Xen: Multiple vulnerabilitiesNessusGentoo Local Security Checks
high
141278Fedora 31 : xen (2020-d46fe34349)NessusFedora Local Security Checks
medium
141270Fedora 33 : xen (2020-306b84fd07)NessusFedora Local Security Checks
medium
141168openSUSE Security Update : xen (openSUSE-2020-1608)NessusSuSE Local Security Checks
medium
141102Fedora 32 : xen (2020-f668e579be)NessusFedora Local Security Checks
medium