Executive Summary

Informations
Name CVE-2019-18421 First vendor Publication 2019-10-31
Vendor Cve Last vendor Modification 2019-11-14

Security-Database Scoring CVSS v3

Cvss vector : CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Overall CVSS Score 7.5
Base Score 7.5 Environmental Score 7.5
impact SubScore 5.9 Temporal Score 7.5
Exploitabality Sub Score 1.6
 
Attack Vector Network Attack Complexity High
Privileges Required Low User Interaction None
Scope Unchanged Confidentiality Impact High
Integrity Impact High Availability Impact High
Calculate full CVSS 3.0 Vectors scores

Security-Database Scoring CVSS v2

Cvss vector : (AV:N/AC:H/Au:S/C:C/I:C/A:C)
Cvss Base Score 7.1 Attack Range Network
Cvss Impact Score 10 Attack Complexity High
Cvss Expoit Score 3.9 Authentication Requires single instance
Calculate full CVSS 2.0 Vectors scores

Detail

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, and so on. These operations may take an arbitrarily large amount of time, and so must be re-startable. Unfortunately, making recursive pagetable promotion and demotion operations restartable is incredibly complicated, and the code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All x86 systems with untrusted PV guests are vulnerable. HVM and PVH guests cannot exercise this vulnerability.

Original Source

Url : http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-18421

CWE : Common Weakness Enumeration

% Id Name
100 % CWE-362 Race Condition

CPE : Common Platform Enumeration

TypeDescriptionCount
Application 18
Os 196

Sources (Detail)

Source Url
BUGTRAQ https://seclists.org/bugtraq/2020/Jan/21
DEBIAN https://www.debian.org/security/2020/dsa-4602
FEDORA https://lists.fedoraproject.org/archives/list/package-announce@lists.fedorapr...
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedorapr...
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedorapr...
GENTOO https://security.gentoo.org/glsa/202003-56
MISC http://xenbits.xen.org/xsa/advisory-299.html
MLIST http://www.openwall.com/lists/oss-security/2019/10/31/3
SUSE http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html

Alert History

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0
Date Informations
2020-05-23 02:26:59
  • First insertion