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XenOperating system

CVE-2023-46835

MEDIUM · 5.5 CVSS v3.1 Published 2024-01-05
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-787

The program writes past the bounds of a buffer, overwriting adjacent memory an attacker can turn to their advantage. Crafted input can overwrite control data and redirect execution. Remediation is validating every index and length before a write, plus modern memory-safety mitigations.

General guidance for the out-of-bounds write class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
XenOperating system
Affected:all versions

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch xenbits.xenproject.org →
Recommended fix Moderate confidence

Upgrade to the specific Xen version indicated in XSA-445 for your stable branch (e.g., Xen 4.17.x, Xen 4.16.x, Xen 4.15.x depending on your branch)

  1. 1. Consult the official Xen Security Advisory (XSA-445) at https://xenbits.xenproject.org/xsa/advisory-445.html for the specific fixed version numbers for your Xen release branch
  2. 2. Identify your current Xen version by running: `xl info | grep xen_version` or `xm info | grep xen_version`
  3. 3. Upgrade your Xen hypervisor to the fixed version specified in XSA-445 for your branch (e.g., xen-4.17, xen-4.16, etc.)
  4. 4. After upgrading, verify the fix is applied by checking that amd_iommu_quarantine_init() now properly detects the number of IOMMU page table levels and creates matching quarantine page tables
  5. 5. Test device assignment and reassignment operations to ensure the quarantine mechanism properly clears pages between assignments
  6. 6. Monitor for any related Xen security advisories that may supersede or complement XSA-445
Caveat Minor: Upgrading the hypervisor requires downtime and may require guest VM restart; ensure guest VMs are properly shut down before upgrade

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-46835 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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