Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Xen | Xen | <= 4.12.1 |
| Debian | Debian Linux | 9.0 |
| Fedoraproject | Fedora | 29 |
Related Weaknesses (CWE)
References
- http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.htmlBroken LinkMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2019/10/31/1Mailing ListPatchThird Party Advisory
- http://xenbits.xen.org/xsa/advisory-296.htmlPatchVendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://seclists.org/bugtraq/2020/Jan/21Mailing ListThird Party Advisory
- https://security.gentoo.org/glsa/202003-56Third Party Advisory
- https://www.debian.org/security/2020/dsa-4602Third Party Advisory
- http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.htmlBroken LinkMailing ListThird Party Advisory
- http://www.openwall.com/lists/oss-security/2019/10/31/1Mailing ListPatchThird Party Advisory
- http://xenbits.xen.org/xsa/advisory-296.htmlPatchVendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro
FAQ
What is CVE-2019-18420?
CVE-2019-18420 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 whic...
How severe is CVE-2019-18420?
CVE-2019-18420 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2019-18420?
Check the references section above for vendor advisories and patch information. Affected products include: Xen Xen, Debian Debian Linux, Fedoraproject Fedora.