CVE-2021-3406Network attack vector

Unauthenticated attestation forgery via unbound TPM keys

Published Feb 25, 2021 · Updated Aug 3, 2024

Trust verification failure in Keylime 5.8.1 and earlier allows remote attackers to forge agent attestations via crafted registration keys. The registrar accepts ek_tpm without proving that it matches ek or ekcert, accepts pub_aik without matching aik_name, and omits Attestation Key attribute checks. Unauthenticated registration permits software-generated keys to sever the TPM-backed trust chain and make untrusted attestations appear valid.

CVSS severity9.8
Critical
EPSS probability0.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Trust verification failure in Keylime 5.8.1 and earlier allows remote attackers to forge agent attestations via crafted registration keys. The registrar accepts ek_tpm without proving that it matches ek or ekcert, accepts pub_aik without matching aik_name, and omits Attestation Key attribute checks. Unauthenticated registration permits software-generated keys to sever the TPM-backed trust chain and make untrusted attestations appear valid.

The record

CVE
CVE-2021-3406
Published
Feb 25, 2021
Updated
Aug 3, 2024
Vendor
Keylime
Product
Keylime
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=5.8.1 and older

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Keylime · Keylimeversion=5.8.1 and older

Published CVSS scores

9.8OSVCVSS:3.1/AV:N/AC:L/PR:N/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

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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