CVE-2019-18420

Description

An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.

Category

6.5
CVSS
Severity: Medium
CVSS 3.1 •
CVSS 2.0 •
EPSS 4.25% 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-296.html patch vendor advisory
http://www.openwall.com/lists/oss-security/2019/10/31/1 patch mailing list third party advisory
http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html vendor advisory broken link 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-2019-18420?
CVE-2019-18420 has been scored as a medium severity vulnerability.
How to fix CVE-2019-18420?
To fix CVE-2019-18420, 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-2019-18420 being actively exploited in the wild?
It is possible that CVE-2019-18420 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~4% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
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