XenserverApplication · Citrix
CVE-2012-3495
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 physdev_get_free_pirq hypercall in arch/x86/physdev.c in Xen 4.1.x and Citrix XenServer 6.0.2 and earlier uses the return value of the get_free_pirq function as an array index without checking that the return value indicates an error, which allows guest OS users to cause a denial of service (invalid memory write and host crash) and possibly gain privileges via unspecified vectors.
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 confidenceThe physdev_get_free_pirq hypercall in Xen 4.1.x and Citrix XenServer 6.0.2 and earlier uses the return value of get_free_pirq() as an array index without validating that it represents a valid IRQ value rather than an error code. This missing bounds check allows guest OS users to trigger invalid memory writes by passing an error value as an array index, leading to host crash (DoS) and potential privilege escalation.
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= 5.0= 5.5= 5.6= 6.0= 4.1.0= 4.1.1= 4.1.2= 4.1.3CVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Complete
AV:L/AC:L/Au:N/C:P/I:P/A:C
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 Xen hypervisor versionRun `xl version` or `xm version` on the host, or for Citrix XenServer run `xe host-version`. Alternatively, check the hypervisor log or boot files for the Xen version string.Affected if The version is Xen 4.1.0, 4.1.1, 4.1.2, or 4.1.3, or Citrix XenServer 5.0, 5.5, 5.6, 6.0, or 6.0.2 or earlier.
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Confirm physdev passthrough is enabledCheck if any guests have PCI passthrough or physdev access configured. On Xen, review VM config files for 'pci' or 'physdev' entries. On XenServer, run `xe vm-list params=other-config` to look for pci or passthrough settings.Affected if Any untrusted guest has direct hardware access via PCI or physdev passthrough enabled.
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Check hypervisor boot parametersReview the Xen hypervisor boot command line (visible in /boot/grub/menu.lst or via `xl dmesg` output). Look for parameters like 'pci-passthrough' or 'dom0=pci-passthrough'.Affected if PCI passthrough or physdev access is enabled at the hypervisor level.
You are affected if running Xen 4.1.0-4.1.3 or XenServer 6.0.2/6.0/5.6/5.5/5.0 AND any untrusted guest has physdev or PCI passthrough enabled.
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 4.1.4 or later, or apply Citrix XenServer patches for versions 6.0.2 and earlier. In the interim, restrict untrusted guests from having direct hardware access via physdev passthrough.
Fix this in Xenserver
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2012-3495 — 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-2012-3495 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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