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XenOperating system

CVE-2017-10920

CRITICAL · 10.0 CVSS v3.0 Published 2017-07-05
Fix available
A fix is available. Upgrade to after 4.8.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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 grant-table feature in Xen through 4.8.x mishandles a GNTMAP_device_map and GNTMAP_host_map mapping, when followed by only a GNTMAP_host_map unmapping, which allows guest OS users to cause a denial of service (count mismanagement and memory corruption) or obtain privileged host OS access, aka XSA-224 bug 1.

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

The grant-table feature in Xen through 4.8.x mishandles GNTMAP_device_map and GNTMAP_host_map mappings when followed by only GNTMAP_host_map unmapping. This causes reference count mismanagement leading to memory corruption and potential privilege escalation from guest OS to host OS, or denial of service.

MitigationApply the Xen security patch (XSA-224) to update to a patched version. Limit or audit guest OS usage of grant table mappings 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
XenOperating system
Affected:<= 4.8.1

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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/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. Verify Xen hypervisor is running
    Run `xl info` or `xm info` to confirm the system is running the Xen hypervisor. If these commands fail or show no Xen-specific information, the system is not a Xen host.
    Affected if The system is not running Xen - no further action needed for this CVE.
  2. Determine installed Xen version
    Run `xl version` or `xm version` to obtain the Xen hypervisor version number. Compare this version against the affected range: any version <= 4.8.1 is vulnerable.
    Affected if The installed Xen version is 4.8.1 or lower.
  3. Confirm grant table availability to guests
    Examine guest configuration files in /etc/xen/ (or /var/lib/xen/) for any guest domains. Grant tables are typically enabled by default for paravirtualized Linux guests. Check for `grant_tables` or `gnttab` related settings in guest configs using `xl cfglist <guestname>` or `xm list -l <guestname>`.
    Affected if Guests are configured with grant table support (the default state for most paravirtualized guests).
  4. Check for active grant table usage
    On the host, monitor for active grant table references: look for `/proc/xen/gnttab` or use `xl list` to identify running guest domains. Active guest domains with grant table access indicate the vulnerable code path may be exercised.
    Affected if Guest domains are running and actively using grant table mappings (GNTMAP_device_map or GNTMAP_host_map operations).

A host is affected if it runs Xen version 4.8.1 or lower AND hosts guest virtual machines that have access to the grant table feature, which is typically enabled by default for paravirtualized guests.

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 4.8.1
Vendor patch xenbits.xen.org →
Interim mitigation

Apply the Xen security patch (XSA-224) to update to a patched version. Limit or audit guest OS usage of grant table mappings until the patch is applied.

Recommended fix High confidence

Xen 4.9.0 or later (e.g., Xen 4.9.x, 4.10.x, 4.11.x stable releases)

  1. 1. Identify all Xen hosts running version 4.8.1 or earlier using: `xl version` or `xm version`
  2. 2. Schedule a maintenance window for Xen hypervisor upgrade
  3. 3. Download Xen 4.9.0 or later from https://downloads.xenproject.org/
  4. 4. Follow Xen upgrade documentation to build and install the new hypervisor
  5. 5. Update all guest VM configurations as needed for compatibility
  6. 6. Reboot hypervisor hosts into the new Xen version
  7. 7. Verify the upgrade by running: `xl version` and confirming the version is 4.9.0 or later
  8. 8. Test guest VM functionality and grant table operations
Caveat Minor configuration adjustments may be needed for guest VMs; review Xen release notes for migration guidance

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

Fix this in Xen Scoped from the published advisory
  • Consultation4.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA3.0 h
19.0 hours of engineering $3,260
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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-2017-10920 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