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VulnerabilityPublished

CVE-2025-66406: smallstep certificates · Incorrect Authorization

Affects smallstep certificatesSource CVE Database V5

0

Not known to be exploited · CVSS 5.0 Medium : upgrade to 0.29.0 when convenient.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score
5.0Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.29.0
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Dec 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade smallstep/certificates to 0.29.0.

Affected software

ProductAffectedFixed in
GitHubsmallstep/certificatespkg:github/smallstep/certificatesOther threatsAffected
  • <0.29.0
Fixed in
  • 0.29.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately upgrade Step CA to version 0.29.0 or later to remediate the improper authorization vulnerability. Until patching is complete, restrict access to the Step CA management interfaces and SSHPOP provisioner to trusted administrators only, minimizing the risk of privilege misuse. Implement strict role-based access controls (RBAC) and monitor logs for unusual certificate revocation activities. Conduct audits of SSH certificate revocation events to detect unauthorized actions promptly. Additionally, consider deploying network segmentation to isolate certificate management infrastructure from general user networks. Employ multi-factor authentication (MFA) for privileged accounts managing Step CA to reduce the risk of credential compromise. Finally, maintain an incident response plan that includes steps for rapid certificate re-issuance and recovery in case of unauthorized revocation.

Description

Step CA is an online certificate authority for secure, automated certificate management for DevOps. Prior to 0.29.0, there is an improper authorization check for SSH certificate revocation. This affects deployments configured with the SSHPOP provisioner. This vulnerability is fixed in 0.29.0.

References

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