CVE-2019-18425

Description

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.

Category

9.8
CVSS
Severity: Critical
CVSS 3.1 •
CVSS 2.0 •
EPSS 4.87% Top 15%
Vendor Advisory opensuse.org Vendor Advisory fedoraproject.org Vendor Advisory fedoraproject.org Vendor Advisory fedoraproject.org Vendor Advisory debian.org Vendor Advisory gentoo.org Vendor Advisory xen.org
Affected: n/a n/a
Published at:
Updated at:

References

Link Tags
http://xenbits.xen.org/xsa/advisory-298.html patch vendor advisory
http://www.openwall.com/lists/oss-security/2019/10/31/2 third party advisory mailing list
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html vendor advisory mailing list third party advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2BQKX7M2RHCWDBKNPX4KEBI3MJIH6AYZ/ vendor advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I5WWPW4BSZDDW7VHU427XTVXV7ROOFFW/ vendor advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IZYATWNUGHRBG6I3TC24YHP5Y3J7I6KH/ vendor advisory
https://www.debian.org/security/2020/dsa-4602 third party advisory vendor advisory
https://seclists.org/bugtraq/2020/Jan/21 third party advisory mailing list
https://security.gentoo.org/glsa/202003-56 third party advisory vendor advisory

Frequently Asked Questions

What is the severity of CVE-2019-18425?
CVE-2019-18425 has been scored as a critical severity vulnerability.
How to fix CVE-2019-18425?
To fix CVE-2019-18425, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2019-18425 being actively exploited in the wild?
It is possible that CVE-2019-18425 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~5% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
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