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XenOperating system

CVE-2023-34322

HIGH · 7.8 CVSS v3.1 Published 2024-01-05
Fix available
A fix is available. Upgrade to 4.15.0 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

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
For migration as well as to work around kernels unaware of L1TF (see XSA-273), PV guests may be run in shadow paging mode. Since Xen itself needs to be mapped when PV guests run, Xen and shadowed PV guests run directly the respective shadow page tables. For 64-bit PV guests this means running on the shadow of the guest root page table. In the course of dealing with shortage of memory in the shadow pool associated with a domain, shadows of page tables may be torn down. This tearing down may include the shadow root page table that the CPU in question is presently running on. While a precaution exists to supposedly prevent the tearing down of the underlying live page table, the time window covered by that precaution isn't large enough.

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 · moderate confidence

A race condition in Xen's shadow paging mode allows the shadow root page table currently in use by a CPU to be torn down during memory shortage in the shadow pool. This occurs because the time window in the existing precaution is insufficient, potentially allowing a PV guest to crash the host or achieve privilege escalation.

MitigationUpdate Xen to the patched version. Alternatively, migrate affected PV guests to HVM mode or disable shadow paging if possible, though this may have compatibility or performance implications.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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:>= 3.2.0, < 4.15.0

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
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Xen hypervisor version
    Run `xl info -r` or `xl info` and look for the xen_version field, or check the package version with `rpm -q xen` (RHEL/CentOS), `dpkg -l xen*` (Debian/Ubuntu), or `zypper se xen` (SLES)
    Affected if The version is 3.2.0 or higher but lower than 4.15.0
  2. Identify paravirtualized (PV) guests
    Run `xl list` to list all guests. PV guests typically show 'PV' in the type column. Run `xl cfgbootloader <guestname>` or inspect guest config files in /etc/xen/ (or /var/lib/xen/images/) for the guest type
    Affected if There are PV guests running, as these are the guests that can trigger shadow paging usage
  3. Check if shadow paging is enabled for guests
    Inspect each PV guest configuration file (typically in /etc/xen/ or /var/lib/xen/) and look for 'shadow_memory' setting, or run `xl list -l <guestname>` and search for 'shadow' in the output
    Affected if shadow_memory is explicitly set or shadow paging is configured for any guest; PV guests may also use shadow paging automatically in certain conditions
  4. Verify shadow paging status in hypervisor runtime
    Run `xl dmesg | grep -i shadow` to check for shadow paging related messages in the hypervisor log, which may indicate active shadow paging usage
    Affected if Shadow paging messages appear in dmesg output indicating the feature is active

You are affected if your Xen version is >= 3.2.0 and < 4.15.0 AND you have PV guests with shadow paging enabled or automatically in use.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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
Upgrade available Upgrade to 4.15.0 or later
Fixed in 4.15.0
Interim mitigation

Update Xen to the patched version. Alternatively, migrate affected PV guests to HVM mode or disable shadow paging if possible, though this may have compatibility or performance implications.

Recommended fix High confidence

Xen 4.15.0 or later

  1. 1. Identify all Xen hosts in the infrastructure running Xen versions >= 3.2.0 and < 4.15.0 using 'xl version' or 'xm version' commands
  2. 2. Schedule a maintenance window for each affected Xen host
  3. 3. Before upgrading, ensure all VMs are safely migrated or shut down according to site policy
  4. 4. Upgrade Xen hypervisor to version 4.15.0 or later by installing the appropriate package for your distribution (e.g., 'apt-get update && apt-get install xen-hypervisor' or equivalent)
  5. 5. Reboot each Xen host to load the new hypervisor
  6. 6. After reboot, verify the running Xen version is >= 4.15.0 using 'xl version'
  7. 7. Resume normal operations by starting/migrating VMs back to the updated hosts
Caveat Upgrading Xen hypervisor requires host reboots; ensure VM downtime is planned or live migration is available. Test the upgrade in a staging environment first if possible.

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

Fix this in Xen Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2023-34322 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data