CVE-2011-2901
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 · uneditedOff-by-one error in the __addr_ok macro in Xen 3.3 and earlier allows local 64 bit PV guest administrators to cause a denial of service (host crash) via unspecified hypercalls that ignore virtual-address bits.
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 confidenceOff-by-one error in the __addr_ok macro in Xen 3.3 and earlier allows local 64-bit PV guest administrators to cause host crash via hypercalls that improperly handle virtual-address bits, bypassing intended address validation checks.
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<= 3.3.0= 3.0.2= 3.0.3= 3.0.4= 3.1.3= 3.1.4= 3.2.0= 3.2.1= 3.2.2= 3.2.3CVSS 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
- Adjacent
- Complexity
- Low
- Authentication
- Single
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:A/AC:L/Au:S/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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Identify if Xen hypervisor is runningRun 'xm info' or 'xl info' to display hypervisor information, or check for xen daemon processes with 'ps aux | grep xen'Affected if Xen is not present - the system is not vulnerable to this Xen-specific flaw
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Determine the installed Xen versionRun 'xm info' or 'xl info' and look for the 'xen_version' field, or run 'xm log' to find version strings at bootAffected if The version matches any of: <= 3.3.0, 3.0.2, 3.0.3, 3.0.4, 3.1.3, 3.1.4, 3.2.0, 3.2.1, 3.2.2, or 3.2.3
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Confirm the environment is a 64-bit PV guestFrom within the guest, run 'uname -m' to check architecture (x86_64 indicates 64-bit), and check if the guest is paravirtualized by examining /proc/xen or running 'xm list' to see guest typeAffected if Running as a 64-bit paravirtualized (PV) guest on affected Xen versions - the specific condition required for exploitation
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Check for administrative privileges in the guestVerify if the user has PV guest admin rights by examining /usr/bin/xen toolstack permissions or checking if the domain has privileges to make hypercallsAffected if The user has PV guest administrative privileges - only administrators with this level of access can trigger the flaw via hypercalls
A system is affected if it runs Xen version 3.0.2 through 3.2.3 or any version <= 3.3.0 as the host, with a 64-bit paravirtualized guest that has administrative privileges capable of issuing hypercalls.
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 version newer than 3.3, or apply vendor patch addressing the __addr_ok macro bounds check. Consider restricting PV guest administrative privileges as a temporary workaround.
- 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-2011-2901 — 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-2011-2901 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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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