CVE-2023-54172 x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction
Linux kernel panics on Hyper-V VMs with IBT enabled due to missing ENDBR instructions, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-54172?
CVE-2023-54172 is a denial of service vulnerability in Linux, published on 30 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
x86/hyperv: Disable IBT when hypercall page lacks ENDBR instruction
On hardware that supports Indirect Branch Tracking (IBT), Hyper-V VMs with ConfigVersion 9.3 or later support IBT in the guest. However, current versions of Hyper-V have a bug in that there's not an ENDBR64 instruction at the beginning of the hypercall page. Since hypercalls are made with an indirect call to the hypercall page, all hypercall attempts fail with an exception and Linux panics.
A Hyper-V fix is in progress to add ENDBR64. But guard against the Linux panic by clearing X86_FEATURE_IBT if the hypercall page doesn't start with ENDBR. The VM will boot and run without IBT.
If future Linux 32-bit kernels were to support IBT, additional hypercall page hackery would be needed to make IBT work for such kernels in a Hyper-V VM.
Which versions are affected by CVE-2023-54172?
How do I fix CVE-2023-54172?
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-2023-54172 being exploited?
There is no known exploitation of CVE-2023-54172 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2023-54172, DEBIAN-CVE-2023-54172, GHSA-3fcf-v62x-cm7w, ROOT-OS-UBUNTU-2204-CVE-2023-54172, UBUNTU-CVE-2023-54172.