CVE-2016-5242
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 p2m_teardown function in arch/arm/p2m.c in Xen 4.4.x through 4.6.x allows local guest OS users with access to the driver domain to cause a denial of service (NULL pointer dereference and host OS crash) by creating concurrent domains and holding references to them, related to VMID exhaustion.
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 · moderate confidenceThe p2m_teardown function in arch/arm/p2m.c in Xen 4.4.x through 4.6.x contains a NULL pointer dereference vulnerability. Local guest OS users with access to the driver domain can cause VMID exhaustion by creating concurrent domains and holding references to them, leading to a NULL pointer dereference that crashes the host OS.
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= 4.4.0= 4.4.1= 4.4.2= 4.4.3= 4.4.4= 4.5.0= 4.5.1= 4.5.2= 4.5.3= 4.6.0= 4.6.1CVSS 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
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:L/AC:H/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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Identify installed Xen versionRun 'xl version' or 'xe --version' or check /usr/sbin/xen* binaries, or look at /var/log/xen/startup.logAffected if The version is 4.4.0 through 4.6.1 (any of: 4.4.0, 4.4.1, 4.4.2, 4.4.3, 4.4.4, 4.5.0, 4.5.1, 4.5.2, 4.5.3, 4.6.0, or 4.6.1)
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Confirm system runs ARM architectureRun 'xl info | grep arch' or 'uname -m' to check the hypervisor architectureAffected if The architecture is ARM (aarch64 or armv7l) since the vulnerability exists in arch/arm/p2m.c
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Verify driver domain configurationCheck Xen configuration files in /etc/xen/ and run 'xl list' to identify domains with driver domain privilegesAffected if A guest domain has access to driver domain functions or untrusted local users can create domains
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Inspect for host crashes or NULL pointer faultsRun 'xl dmesg' or check /var/log/xen/ for crash logs containing 'p2m_teardown' or NULL pointer dereference errorsAffected if Crash logs show NULL pointer dereference in p2m_teardown function or VMID exhaustion messages
You are affected if running Xen 4.4.0-4.6.1 on ARM architecture with guest access to a driver domain, or if crash logs show the specific p2m_teardown NULL dereference.
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 Xen to version 4.6.1 or later. Alternatively, restrict or eliminate local guest OS access to the driver domain to prevent untrusted users from triggering the vulnerability.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2016-5242 — 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-2016-5242 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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- Version or environment caveats, and links to real fixes
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