CVE-2021-28692
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 · uneditedinappropriate x86 IOMMU timeout detection / handling IOMMUs process commands issued to them in parallel with the operation of the CPU(s) issuing such commands. In the current implementation in Xen, asynchronous notification of the completion of such commands is not used. Instead, the issuing CPU spin-waits for the completion of the most recently issued command(s). Some of these waiting loops try to apply a timeout to fail overly-slow commands. The course of action upon a perceived timeout actually being detected is inappropriate: - on Intel hardware guests which did not originally cause the timeout may be marked as crashed, - on AMD hardware higher layer callers would not be notified of the issue, making them continue as if the IOMMU operation succeeded.
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's x86 IOMMU implementation, the CPU spin-waits for IOMMU command completion rather than using asynchronous notifications. When timeout loops detect a perceived timeout, the handling is flawed: on Intel hardware, unrelated guests may be incorrectly marked as crashed, while on AMD hardware, higher-layer callers aren't notified and continue assuming the IOMMU operation succeeded.
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>= 3.2.0CVSS 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
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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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Confirm Xen hypervisor is runningRun `xl version` or `xm version` to verify Xen is the active hypervisor. Alternatively, check `dmesg | grep -i xen` for Xen boot messages.Affected if The system is running Xen as the hypervisor platform
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Check Xen version against affected rangeRun `xl version` or `xm version` to obtain the installed Xen version number, then compare it to the affected range of >= 3.2.0.Affected if The Xen version is 3.2.0 or higher
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Verify IOMMU is enabled in the Xen environmentRun `xl dmesg | grep -i iommu` or check boot parameters in `/boot/grub/grub.conf` for `iommu=` settings. On the host, also check `xl info` for iommu information.Affected if IOMMU support is enabled and active in the Xen configuration
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Confirm x86 architecture is in useVerify the host system uses x86 (32-bit or 64-bit) processors by running `uname -m` or checking BIOS/UEFI system information.Affected if The Xen hosts run on x86 (Intel or AMD) hardware
The environment is affected if it runs Xen version 3.2.0 or higher with IOMMU enabled on x86 architecture, as the flaw exists in the IOMMU command completion timeout handling code path.
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 dataApply the Xen security patch for CVE-2021-28692 which corrects the timeout detection logic and ensures proper crash notification on Intel and error propagation on AMD hardware.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 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 $7,616.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-28692 — 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-2021-28692 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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