Linux KernelOperating system · Linux
CVE-2009-3722
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 handle_dr function in arch/x86/kvm/vmx.c in the KVM subsystem in the Linux kernel before 2.6.31.1 does not properly verify the Current Privilege Level (CPL) before accessing a debug register, which allows guest OS users to cause a denial of service (trap) on the host OS via a crafted application.
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 handle_dr function in KVM's VMX implementation fails to verify the Current Privilege Level (CPL) before allowing access to debug registers. This allows a malicious guest OS user to trigger a trap on the host OS by crafting an application that accesses debug registers improperly, causing a 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
Linux KernelOperating system
<= 2.6.31= 2.6.0= 2.6.1= 2.6.2= 2.6.3= 2.6.4= 2.6.5= 2.6.6= 2.6.7= 2.6.8= 2.6.8.1= 2.6.9CVSS 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
- M
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:M/Au:N/C:N/I:N/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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Check the running kernel versionRun 'uname -r' or 'cat /proc/version' to obtain the kernel versionAffected if The kernel version is 2.6.31 or earlier, matching the listed vulnerable versions (2.6.0 through 2.6.31)
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Verify KVM VMX kernel modules are loadedRun 'lsmod | grep -E "kvm|vmx"' to check if KVM and VMX-related modules are loadedAffected if The kvm_intel (for Intel VT-x) or kvm_amd (for AMD-V) modules with VMX support are loaded, indicating the vulnerable code path is active
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Confirm hardware virtualization support is presentCheck /proc/cpuinfo for 'vmx' (Intel) or 'svm' (AMD) flags: 'grep -E "vmx|svm" /proc/cpuinfo'Affected if The processor supports and exposes hardware virtualization (VMX for Intel, SVM for AMD), meaning the vulnerable VMX implementation could be used
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Identify if KVM is in use on the systemRun 'ps aux | grep -E "qemu|kvm"' or check for KVM-related processes and libvirt servicesAffected if The host is running virtual machines via KVM, which activates the vulnerable handle_dr function in the VMX implementation
The system is affected if it runs a Linux kernel version 2.6.31 or earlier, has KVM with VMX hardware virtualization enabled, and is hosting virtual machines - allowing a malicious guest to trigger the unprivileged debug register access and cause host denial of service.
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 Linux kernel to version 2.6.31.1 or later which contains the proper CPL verification fix. Alternatively, ensure virtualization hosts are not running untrusted guest VMs with this kernel version.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 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 $4,416.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-3722 — 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-2009-3722 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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