CVE-2023-46835 x86/AMD: mismatch in IOMMU quarantine page table levels
A page table level mismatch in Xen's IOMMU quarantine allows devices to access uncleared memory, potentially leaking data or escalating privileges.
- 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-2023-46835?
CVE-2023-46835 is a medium-severity memory corruption vulnerability in Xen Xen, published on 5 Jan 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The current setup of the quarantine page tables assumes that the quarantine domain (dom_io) has been initialized with an address width of DEFAULT_DOMAIN_ADDRESS_WIDTH (48) and hence 4 page table levels.
However dom_io being a PV domain gets the AMD-Vi IOMMU page tables levels based on the maximum (hot pluggable) RAM address, and hence on systems with no RAM above the 512GB mark only 3 page-table levels are configured in the IOMMU.
On systems without RAM above the 512GB boundary amd_iommu_quarantine_init() will setup page tables for the scratch page with 4 levels, while the IOMMU will be configured to use 3 levels only, resulting in the last page table directory (PDE) effectively becoming a page table entry (PTE), and hence a device in quarantine mode gaining write access to the page destined to be a PDE.
Due to this page table level mismatch, the sink page the device gets read/write access to is no longer cleared between device assignment, possibly leading to data leaks.
Weakness: CWE-787
Which versions are affected by CVE-2023-46835?
It affects 1 product.
Products include Xen Xen.
How do I fix CVE-2023-46835?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2023-46835 being exploited?
There is no known exploitation of CVE-2023-46835 in the wild and no public exploit code.
Other vulnerabilities in Xen Xen
Sources
Also known as ALPINE-CVE-2023-46835, DEBIAN-CVE-2023-46835, GHSA-c2mm-wq7p-rpm8, UBUNTU-CVE-2023-46835.