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XenOperating system

CVE-2017-10921

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 does not ensure sufficient type counts for a GNTMAP_device_map and GNTMAP_host_map mapping, 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 2.

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

Xen's grant-table feature through version 4.8.x fails to enforce sufficient type counts for GNTMAP_device_map and GNTMAP_host_map mappings, allowing a malicious guest OS user to manipulate reference counting, cause memory corruption and denial of service, or escalate privileges to the host OS.

MitigationApply Xen security patches for XSA-224; upgrade to a patched Xen version beyond 4.8.x or apply vendor-specific patches. Coordinate maintenance window as hypervisor update requires VM migration considerations.

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. Determine installed Xen hypervisor version
    Run `xl version` or `xm version` in dom0, or check the Xen package version with `rpm -q xen` or `dpkg -l xen-utils` depending on your Linux distribution
    Affected if The version is Xen 4.8.x or lower, specifically any version up to and including 4.8.1
  2. Confirm grant-table feature is in use
    Check for running paravirtualized (PV) guests using `xl list` or `xm list`. Grant tables are primarily used by PV guests; also check `xl info` for hypervisor capabilities listing gnttab
    Affected if Any paravirtualized guest is running on the Xen hypervisor, as PV guests rely on grant-table mechanism for shared memory with the host
  3. Verify GNTMAP mappings are accessible
    Check guest configuration files in /etc/xen/ for device or host mapping parameters. For guests with PV drivers enabled, the grant-table interface is automatically used for device and memory sharing
    Affected if The hypervisor runs PV guests with paravirtualized drivers loaded, which triggers use of GNTMAP_device_map and GNTMAP_host_map mappings
  4. Identify if host privileges are reachable
    Review Xen hypervisor logs in /var/log/xen/ for any grant-table related warnings or errors, and check dom0 kernel logs with `dmesg` for grant-table activity
    Affected if The hypervisor has not been patched for XSA-224 and is running vulnerable grant-table code with untrusted guest workloads present

You are affected if your Xen hypervisor version is 4.8.1 or any earlier 4.8.x release AND you run paravirtualized guest VMs, as the grant-table vulnerability in the GNTMAP_device_map and GNTMAP_host_map code paths is exposed.

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 Xen security patches for XSA-224; upgrade to a patched Xen version beyond 4.8.x or apply vendor-specific patches. Coordinate maintenance window as hypervisor update requires VM migration considerations.

Recommended fix High confidence

Xen 4.8.2 or later stable release; alternatively Xen 4.9.x/4.10.x/4.11.x if supported by your infrastructure

  1. 1. Identify the current Xen version installed: `xl version` or `xm version`
  2. 2. Back up all critical VM configurations and data
  3. 3. Check the Xen project repository or your distribution's package manager for Xen 4.8.2 or later
  4. 4. For Debian/Ubuntu: `apt-get update && apt-get install xen-hypervisor-4.8` or subsequent version
  5. 5. For RHEL/CentOS: `yum update xen-xen` or use the distribution's virtualization repo
  6. 6. For Gentoo: `emerge --sync && emerge -av xen`
  7. 7. After upgrade, restart the host (dom0) to load the new hypervisor
  8. 8. Verify the new version is running: `xl version`
Caveat Hypervisor upgrades require host reboots; ensure VM downtime is planned; test critical workloads on a staging system before production rollout

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 / QA4.0 h
22.0 hours of engineering $3,860
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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-2017-10921 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