CVE-2025-66406Network attack vector

SSH certificate revocation via unbound authorization token

Published Dec 3, 2025 · Updated Dec 3, 2025

Incorrect authorization in Smallstep step-ca 0.28.4 and earlier allows remote authenticated users to revoke any SSH certificate. The SSHPOP revocation path accepts a valid token without confirming that it is bound to the target certificate's serial number. Exploitation requires CA endpoint access, a valid SSH certificate, and the target serial number; revocation prevents future certificate renewals.

CVSS severity5.0
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Smallstep step-ca 0.28.4 and earlier allows remote authenticated users to revoke any SSH certificate. The SSHPOP revocation path accepts a valid token without confirming that it is bound to the target certificate's serial number. Exploitation requires CA endpoint access, a valid SSH certificate, and the target serial number; revocation prevents future certificate renewals.

The record

CVE
CVE-2025-66406
Published
Dec 3, 2025
Updated
Dec 3, 2025
Vendor
Smallstep
Product
step-ca
Classifications
CWE-863, CWE-285, T1531
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 3, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 3, 2025Record 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=< 0.29.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Smallstep · step-caversion=< 0.29.0

Published CVSS scores

5.0GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
CWE-285Improper Authorization
T1531Account Access Removal

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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