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Debian LinuxOperating system · Debian

CVE-2022-42333

HIGH · 8.6 CVSS v3.1 Published 2023-03-21
Fix available
A fix is available. Upgrade to after 4.17.0 or later.
See remediation →
95/100
Remediation priority · Urgent
Remotely reachable No privileges 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
x86/HVM pinned cache attributes mis-handling T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] To allow cachability control for HVM guests with passed through devices, an interface exists to explicitly override defaults which would otherwise be put in place. While not exposed to the affected guests themselves, the interface specifically exists for domains controlling such guests. This interface may therefore be used by not fully privileged entities, e.g. qemu running deprivileged in Dom0 or qemu running in a so called stub-domain. With this exposure it is an issue that - the number of the such controlled regions was unbounded (CVE-2022-42333), - installation and removal of such regions was not properly serialized (CVE-2022-42334).

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 · high confidence

In Xen hypervisor's x86/HVM subsystem, an interface allows controlling cache attributes for HVM guests with passed-through devices. This interface (accessible to deprivileged entities like qemu in Dom0 or stub-domains) lacks bounds checking on the number of cache region entries that can be created, allowing an attacker to exhaust resources by creating an unbounded number of pinned cache attribute regions.

MitigationApply Xen security patches to introduce bounds checking on the number of cachability control regions. Consider restricting or auditing usage of this interface by deprivileged entities until the patch is applied.

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
Debian LinuxOperating system
Affected:= 11.0
FedoraOperating system
Affected:= 37= 38
XenOperating system
Affected:>= 4.11.0, <= 4.17.0

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/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. Identify the installed Xen hypervisor version
    Run 'xl info' or 'xm info' and look for the 'xen_version' field, or check the package version with 'dpkg -l | grep xen' on Debian or 'rpm -q xen' on Fedora
    Affected if The version falls within the range 4.11.0 to 4.17.0 inclusive
  2. Determine if HVM (Hardware Virtual Machine) guests are in use
    Run 'xl list' or 'xm list' and check the 'HVM' column, or inspect guest configuration files in /etc/xen/ for 'builder = "hvm"'
    Affected if Any HVM guests are configured or running
  3. Check for PCI passthrough devices assigned to HVM guests
    Run 'xl pci-list <guestname>' or 'xm pci-list <guestname>' for each HVM guest, or examine guest config files for 'pci' entries
    Affected if HVM guests have PCI devices passed through to them
  4. Monitor for resource exhaustion from cache region creation
    Check Xen logs in /var/log/xen/ for repeated messages containing 'cache' or 'cacheline', or monitor for system slowdown/unavailability of domain creation that may indicate resource depletion
    Affected if Unusual log patterns or inability to create/start domains are observed after deprivileged entities have accessed HVM cache control interfaces

A system is affected if it runs Xen version 4.11.0 through 4.17.0 with active HVM guests that have passed-through devices, where deprivileged entities can access the cache attribute control interface.

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 a release after 4.17.0
Interim mitigation

Apply Xen security patches to introduce bounds checking on the number of cachability control regions. Consider restricting or auditing usage of this interface by deprivileged entities until the patch is applied.

Recommended fix Moderate confidence

Xen 4.18.0 or later; Debian 11 and Fedora 37/38 should receive updated Xen packages via their respective update channels

  1. Identify the Xen hypervisor version currently installed (e.g., `xl info`, `xm info`, or `dmesg | grep -i xen`)
  2. For Debian 11 (bullseye): Check for and apply Xen updates via `apt update && apt upgrade` or migrate to a supported Xen version
  3. For Fedora 37/38: Check for and apply Xen updates via `dnf update` or migrate to a supported Xen version
  4. For Xen: Upgrade to Xen 4.18.0 or later where the unbounded resource allocation issue is addressed
  5. After upgrade, verify the new Xen version is running and validate that cache attribute region limits are properly enforced
Caveat Upgrading Xen hypervisor may require rebooting the host and can impact running VMs; ensure proper VM migration or shutdown procedures are in place before upgrading

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

Fix this in Debian Linux Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA6.0 h
34.0 hours of engineering $5,940
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Scan for this in your stack

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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-2022-42333 in production — separate from our analysis above.

No notes yet

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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