An issue was discovered in Xen through 4.10.x. Certain PV MMU operations may take a long time to process. For that reason Xen explicitly checks for the need to preempt the current vCPU at certain points. A few rarely taken code paths did bypass such checks. By suitably enforcing the conditions through its own page table contents, a malicious guest may cause such bypasses to be used for an unbounded number of iterations. A malicious or buggy PV guest may cause a Denial of Service (DoS) affecting the entire host. Specifically, it may prevent use of a physical CPU for an indeterminate period of time. All Xen versions from 3.4 onwards are vulnerable. Xen versions 3.3 and earlier are vulnerable to an even wider class of attacks, due to them lacking preemption checks altogether in the affected code paths. Only x86 systems are affected. ARM systems are not affected. Only multi-vCPU x86 PV guests can leverage the vulnerability. x86 HVM or PVH guests as well as x86 single-vCPU PV ones cannot leverage the vulnerability.
Published 2018-07-02 17:29:00
Updated 2019-10-03 00:03:26
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Denial of service

Exploit prediction scoring system (EPSS) score for CVE-2018-12891

0.06%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 25 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2018-12891

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
4.9
MEDIUM AV:L/AC:L/Au:N/C:N/I:N/A:C
3.9
6.9
NIST
6.5
MEDIUM CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
2.0
4.0
NIST

References for CVE-2018-12891

Products affected by CVE-2018-12891

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