CVE-2024-45818 Deadlock in x86 HVM standard VGA handling
A deadlock in Xen hypervisor VGA handling allows guest users to cause a denial of service by triggering specific memory access patterns.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-45818?
CVE-2024-45818 is a medium-severity denial of service vulnerability in Xen Xen, published on 19 Dec 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The hypervisor contains code to accelerate VGA memory accesses for HVM guests, when the (virtual) VGA is in "standard" mode. Locking involved there has an unusual discipline, leaving a lock acquired past the return from the function that acquired it. This behavior results in a problem when emulating an instruction with two memory accesses, both of which touch VGA memory (plus some further constraints which aren't relevant here). When emulating the 2nd access, the lock that is already being held would be attempted to be re-acquired, resulting in a deadlock.
This deadlock was already found when the code was first introduced, but was analysed incorrectly and the fix was incomplete. Analysis in light of the new finding cannot find a way to make the existing locking discipline work.
In staging, this logic has all been removed because it was discovered to be accidentally disabled since Xen 4.7. Therefore, we are fixing the locking problem by backporting the removal of most of the feature. Note that even with the feature disabled, the lock would still be acquired for any accesses to the VGA MMIO region.
Weakness: CWE-667
Which versions are affected by CVE-2024-45818?
It affects 1 product.
Products include Xen Xen.
How do I fix CVE-2024-45818?
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-2024-45818 being exploited?
There is no known exploitation of CVE-2024-45818 in the wild and no public exploit code.
Other vulnerabilities in Xen Xen
Sources
Also known as ALPINE-CVE-2024-45818, DEBIAN-CVE-2024-45818, GHSA-9ppw-wh7x-2qc9, UBUNTU-CVE-2024-45818.