CVE-2021-26311
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 · uneditedIn the AMD SEV/SEV-ES feature, memory can be rearranged in the guest address space that is not detected by the attestation mechanism which could be used by a malicious hypervisor to potentially lead to arbitrary code execution within the guest VM if a malicious administrator has access to compromise the server hypervisor.
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 confidenceAMD SEV/SEV-ES (Secure Encrypted Virtualization) has a vulnerability where memory rearrangement in the guest address space is not detected by the attestation mechanism. A compromised hypervisor can exploit this to potentially achieve arbitrary code execution within the guest VM.
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 dataall versionsall versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/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 the CPU modelRun 'lscpu' or 'cat /proc/cpuinfo' and look for the processor model name in the 'Model name' fieldAffected if The CPU model is one of the following: AMD Epyc 7232p, 7251, 7252, 7261, 7262, 7272, 7281, or 7282 (any version)
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Verify SEV/SEV-ES is enabled in the hypervisorCheck the hypervisor configuration (e.g., for KVM/QEMU, inspect the XML configuration via 'virsh dumpxml <vm_name>' and look for the <sev> element, or check QEMU command-line arguments for SEV/SEV-ES parameters such as 'sev=' or 'sev-es='Affected if SEV or SEV-ES is enabled in the VM configuration (the <sev> or <sev-es> element is present with active='yes', or the VM launch includes SEV/SEV-ES parameters)
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Check for active SEV/SEV-ES VMsFor libvirt/KVM environments, run 'virsh list --all' and for each VM inspect its XML with 'virsh dumpxml <vm_name>' to see if SEV/SEV-ES is actively in useAffected if Any VM is running with SEV or SEV-ES encryption actively enabled (visible in the active VM configuration)
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Verify SEV/SEV-ES kernel supportCheck /sys/kernel/debug/sev or /sys/firmware/arc/uefi-cod-mm for SEV capability files, or run 'kvm-ok' (if available) to confirm KVM SEV support is present in the kernelAffected if The system reports SEV or SEV-ES as available in the kernel debug or capability interfaces
A system is affected if it uses an affected AMD Epyc CPU model (7232p, 7251, 7252, 7261, 7262, 7272, 7281, or 7282) and has SEV or SEV-ES actively enabled for any virtual machine, allowing a compromised hypervisor to potentially manipulate guest memory without detection.
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 AMD-provided microcode/hypervisor patches for SEV/SEV-ES that address the attestation gap; verify guest VM attestation processes are functioning correctly after updates.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26311 — 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-2021-26311 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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