An issue was discovered in Xen through 4.12.x allowing 32-bit PV guest OS users to gain guest OS privileges by installing and using descriptors. There is missing descriptor table limit checking in x86 PV emulation. When emulating certain PV guest operations, descriptor table accesses are performed by the emulating code. Such accesses should respect the guest specified limits, unless otherwise guaranteed to fail in such a case. Without this, emulation of 32-bit guest user mode calls through call gates would allow guest user mode to install and then use descriptors of their choice, as long as the guest kernel did not itself install an LDT. (Most OSes don't install any LDT by default). 32-bit PV guest user mode can elevate its privileges to that of the guest kernel. Xen versions from at least 3.2 onwards are affected. Only 32-bit PV guest user mode can leverage this vulnerability. HVM, PVH, as well as 64-bit PV guests cannot leverage this vulnerability. Arm systems are unaffected.
Published 2019-10-31 14:15:12
Updated 2023-03-29 18:20:55
Source MITRE
View at NVD,   CVE.org

Exploit prediction scoring system (EPSS) score for CVE-2019-18425

Probability of exploitation activity in the next 30 days: 1.37%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 86 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2019-18425

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
9.3
HIGH AV:N/AC:M/Au:N/C:C/I:C/A:C
8.6
10.0
NIST
9.8
CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.9
5.9
NIST

CWE ids for CVE-2019-18425

  • The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
    Assigned by: nvd@nist.gov (Primary)

References for CVE-2019-18425

Products affected by CVE-2019-18425

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