CVE-2019-18420 Denial of service in n/a
Malicious x86 PV guests can crash the Xen hypervisor via a specific hypercall, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2019-18420?
CVE-2019-18420 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 31 Oct 2019. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-134
Which versions are affected by CVE-2019-18420?
It affects 3 products.
Products include Debian Debian Linux, Fedoraproject Fedora, Xen Xen.
How do I fix CVE-2019-18420?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2019-18420 being exploited?
There is no known exploitation of CVE-2019-18420 in the wild and no public exploit code.
Other vulnerabilities in Debian Debian Linux
Sources
Also known as ALPINE-CVE-2019-18420, DEBIAN-CVE-2019-18420, GHSA-54p2-qq73-f565, UBUNTU-CVE-2019-18420.