Executive Summary

Name CVE-2019-19578 First vendor Publication 2019-12-11
Vendor Cve Last vendor Modification 2020-08-24

Security-Database Scoring CVSS v3

Cvss vector : CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Overall CVSS Score 8.8
Base Score 8.8 Environmental Score 8.8
impact SubScore 6 Temporal Score 8.8
Exploitabality Sub Score 2
Attack Vector Local Attack Complexity Low
Privileges Required Low User Interaction None
Scope Changed Confidentiality Impact High
Integrity Impact High Availability Impact High
Calculate full CVSS 3.0 Vectors scores

Security-Database Scoring CVSS v2

Cvss vector : (AV:L/AC:L/Au:N/C:C/I:C/A:C)
Cvss Base Score 7.2 Attack Range Local
Cvss Impact Score 10 Attack Complexity Low
Cvss Expoit Score 3.9 Authentication None Required
Calculate full CVSS 2.0 Vectors scores


An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via degenerate chains of linear pagetables, because of an incorrect fix for CVE-2017-15595. "Linear pagetables" is a technique which involves either pointing a pagetable at itself, or to another pagetable of the same or higher level. Xen has limited support for linear pagetables: A page may either point to itself, or point to another pagetable of the same level (i.e., L2 to L2, L3 to L3, and so on). XSA-240 introduced an additional restriction that limited the "depth" of such chains by allowing pages to either *point to* other pages of the same level, or *be pointed to* by other pages of the same level, but not both. To implement this, we keep track of the number of outstanding times a page points to or is pointed to another page table, to prevent both from happening at the same time. Unfortunately, the original commit introducing this reset this count when resuming validation of a partially-validated pagetable, incorrectly dropping some "linear_pt_entry" counts. If an attacker could engineer such a situation to occur, they might be able to make loops or other arbitrary chains of linear pagetables, as described in XSA-240. A malicious or buggy PV guest may cause the hypervisor to crash, resulting in Denial of Service (DoS) affecting the entire host. Privilege escalation and information leaks cannot be excluded. All versions of Xen are vulnerable. Only x86 systems are affected. Arm systems are not affected. Only x86 PV guests can leverage the vulnerability. x86 HVM and PVH guests cannot leverage the vulnerability. Only systems which have enabled linear pagetables are vulnerable. Systems which have disabled linear pagetables, either by selecting CONFIG_PV_LINEAR_PT=n when building the hypervisor, or adding pv-linear-pt=false on the command-line, are not vulnerable.

Original Source

Url : http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-19578

CWE : Common Weakness Enumeration

% Id Name
100 % CWE-682 Incorrect Calculation

CPE : Common Platform Enumeration

Application 18
Os 1
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...
GENTOO https://security.gentoo.org/glsa/202003-56
MISC https://xenbits.xen.org/xsa/advisory-309.html
SUSE http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00011.html

Alert History

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Date Informations
2020-09-03 01:26:40
  • Multiple Updates
2020-05-23 02:28:41
  • First insertion