XenserverApplication · Citrix
CVE-2016-9637
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 · uneditedThe (1) ioport_read and (2) ioport_write functions in Xen, when qemu is used as a device model within Xen, might allow local x86 HVM guest OS administrators to gain qemu process privileges via vectors involving an out-of-range ioport access.
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 confidenceIn Xen hypervisors using qemu as the device model for HVM guests, the ioport_read and ioport_write functions lack proper bounds checking on ioport access. Local administrators in x86 HVM guest VMs can trigger out-of-range ioport accesses to escape guest containment and execute code with qemu process privileges on the host, achieving privilege escalation from guest root to host-level qemu process.
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
XenserverApplication
= 6.0.2= 6.2.0= 6.5= 7.0CVSS 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
- High
- Privileges
- High
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:L/AC:H/PR:H/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 checksWork through these to decide whether this CVE applies to you.
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Identify the hypervisor productRun 'xe host-list' or check /etc/redhat-release to confirm the system is running Citrix XenserverAffected if The hypervisor is not Citrix Xenserver (this CVE specifically affects Citrix Xenserver)
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Check Xenserver versionRun 'xe host-version' or check 'cat /etc/xensource-version' to determine the installed Xenserver versionAffected if The version is exactly 6.0.2, 6.2.0, 6.5, or 7.0 (these are the only affected versions listed)
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Confirm HVM guest usageRun 'xe vm-list' and look for VMs with 'HVM' in the guest metrics or check the VM platform: 'hvm' parameterAffected if HVM (Hardware Virtual Machine) guests are running or configured on the host (the vulnerability only affects HVM guests, not PV guests)
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Check for active qemu processRun 'ps aux | grep qemu' on the host to verify qemu-dm (device model) processes are running for HVM guestsAffected if qemu-dm processes are active for HVM guests on the host (the vulnerable ioport functions are in the qemu device model)
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Verify patch statusCheck Xen and qemu package versions against vendor advisories for CVE-2016-9637, or review the Xen hypervisor version with 'xl version'Affected if The installed Xen and qemu packages have not been patched for the ioport bounds checking vulnerability (unpatched versions retain the flaw)
A system is affected if it runs Citrix Xenserver version 6.0.2, 6.2.0, 6.5, or 7.0 with active HVM guests, and the Xen/qemu packages remain unpatched for CVE-2016-9637.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataApply Xen security patches addressing the ioport access bounds checking vulnerability; ensure Xen and qemu versions are updated to patched releases. Restrict local administrative access to HVM guests as a defense-in-depth measure until patching is complete.
Fix this in Xenserver
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,888.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-9637 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2016-9637 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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