CVE-2018-5244
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 · uneditedIn Xen 4.10, new infrastructure was introduced as part of an overhaul to how MSR emulation happens for guests. Unfortunately, one tracking structure isn't freed when a vcpu is destroyed. This allows guest OS administrators to cause a denial of service (host OS memory consumption) by rebooting many times.
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 4.10, the MSR (Model Specific Register) emulation infrastructure was overhauled, but a tracking structure is not properly freed when a vCPU is destroyed. This creates a memory leak where each guest vCPU reboot accumulates unfreed memory on the host, leading to eventual memory exhaustion and denial of service.
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>= 4.10.0CVSS 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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:L/AC:L/PR:L/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 checksWork through these to decide whether this CVE applies to you.
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Verify Xen hypervisor versionRun `xl info -r` or `xm info -r` to display the hypervisor version. Alternatively, check the kernel log or `/proc/xen/version` if accessible from dom0.Affected if The reported Xen version is 4.10.0 or higher.
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Confirm the host is running XenCheck for the presence of Xen-specific processes or modules: run `ps aux | grep xen` or check `ls /proc/xen/` from dom0.Affected if The system is not running Xen as the hypervisor (e.g., KVM, VMware).
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Identify active guest domains with vCPUsRun `xl list` or `xm list` to enumerate running guest domains and their vCPU counts.Affected if No guest domains with vCPUs are running; the leak only manifests when guest vCPUs are created and destroyed.
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Monitor host memory usage over timeObserve host physical memory usage (e.g., `xl top` or `free -m` in dom0) and track whether free memory decreases as guest vCPUs are rebooted or destroyed.Affected if Host memory steadily decreases with each guest vCPU reboot or destruction cycle, indicating the leak is active.
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Check for MSR emulation usageReview guest configuration files in /etc/xen/ for any MSR-specific emulation settings or whitelist entries. MSR emulation is used when guests access model-specific registers.Affected if Guests are configured to use MSR emulation (the vulnerable code path) and undergo vCPU reboots.
You are affected if running Xen 4.10.0 or higher with active guest domains that reboot or have vCPUs destroyed, and host memory shows progressive depletion correlated with guest vCPU activity.
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 dataUpgrade to Xen 4.10.x with the fix applied, or apply the vendor patch that adds proper cleanup of the MSR emulation tracking structure in the vCPU destruction path. Consider limiting guest reboot frequency as a temporary mitigation.
- Consultation4.0 h
- Implementation8.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-5244 — 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-2018-5244 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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