Vulnerability in Xen
CVE-2019-18420
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.025 (84.2th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 84.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.025 · newest: 0.025 · change: 0.000
Affected products
- Xen
- Debian Linux — versions 9.0, 10.0
- Fedoraproject Fedora — versions 29, 30, 31
Weakness classification (CWE)
References
- xenbits.xen.org/xsa/advisory-296.html (Patch, Vendor Advisory)
- www.openwall.com/lists/oss-security/2019/10/31/1 (mailing-list, Patch, Mailing List, Third Party Advisory)
- lists.opensuse.org/opensuse-security-announce/2019-11/msg00037.html (vendor-advisory, Mailing List, Third Party Advisory, Broken Link)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- www.debian.org/security/2020/dsa-4602 (vendor-advisory, Third Party Advisory)
- seclists.org/bugtraq/2020/Jan/21 (mailing-list, Mailing List, Third Party Advisory)
- security.gentoo.org/glsa/202003-56 (vendor-advisory, Third Party Advisory)
Frequently asked questions
- What is CVE-2019-18420?
- CVE-2019-18420 is a medium-severity vulnerability in Xen, classified under Use of Externally-Controlled Format String. CVSS score: 6.5/10. Published 2019-10-31.
- How severe is CVE-2019-18420?
- Medium severity. CVSS v3 base score is 6.5 out of 10.