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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2019-18421 Detail

Description

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.


Metrics

 
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CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html Mailing List  Third Party Advisory 
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html Mailing List  Third Party Advisory 
http://www.openwall.com/lists/oss-security/2019/10/31/3 Mailing List  Patch  Third Party Advisory 
http://www.openwall.com/lists/oss-security/2019/10/31/3 Mailing List  Patch  Third Party Advisory 
http://xenbits.xen.org/xsa/advisory-299.html Patch  Vendor Advisory 
http://xenbits.xen.org/xsa/advisory-299.html Patch  Vendor Advisory 
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/
https://seclists.org/bugtraq/2020/Jan/21 Mailing List  Third Party Advisory 
https://seclists.org/bugtraq/2020/Jan/21 Mailing List  Third Party Advisory 
https://security.gentoo.org/glsa/202003-56 Third Party Advisory 
https://security.gentoo.org/glsa/202003-56 Third Party Advisory 
https://www.debian.org/security/2020/dsa-4602 Third Party Advisory 
https://www.debian.org/security/2020/dsa-4602 Third Party Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') cwe source acceptance level NIST  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

13 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2019-18421
NVD Published Date:
10/31/2019
NVD Last Modified:
11/20/2024
Source:
MITRE