CVE-2021-26311Public exploitNetwork attack vector

Guest code execution via permutation-agnostic attestation

Published May 13, 2021 · Updated Sep 17, 2024

Attestation bypass in AMD SEV and SEV-ES allows attackers to execute arbitrary code inside an attested guest VM. The attestation measurement is permutation-agnostic, so a compromised hypervisor can reorder measured guest-memory blocks without changing the reported measurement and can assemble a ROP chain during UEFI startup. Exploitation requires administrator control of the server hypervisor and grants control of the guest operating system despite successful attestation.

CVSS severity7.2
High
EPSS probability1.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Attestation bypass in AMD SEV and SEV-ES allows attackers to execute arbitrary code inside an attested guest VM. The attestation measurement is permutation-agnostic, so a compromised hypervisor can reorder measured guest-memory blocks without changing the reported measurement and can assemble a ROP chain during UEFI startup. Exploitation requires administrator control of the server hypervisor and grants control of the guest operating system despite successful attestation.

The record

CVE
CVE-2021-26311
Published
May 13, 2021
Updated
Sep 17, 2024
Vendor
AMD
Product
AMD Secure Encrypted Virtualization (SEV)
Classifications
CWE-77, T1068
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. May 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <SEV-SNP

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

AMD · AMD Secure Encrypted Virtualization (SEV)version=unspecified <SEV-SNP

Published CVSS scores

9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C
7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-77Improper Neutralization of Special Elements used in a Command ('Command Injection')
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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