No exploitation reportedFix available

CVE-2025-66406

Q: Is CVE-2025-66406 actively exploited?

Active exploitation of CVE-2025-66406 has not been confirmed. Its EPSS score was 0.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2025-66406?

CVE-2025-66406 has a CVSS v3 base score of 5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:H.

No exploitation reported by the sources we read.

Published2025-12-03
Fixed in0.29.0
WeaknessCWE-863

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2025-12-0320:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-66406?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-66406?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

OSV

smallstep/certificates

Branch	Affected	Fixed in	Source
0.29	< 0.29.0	0.29.0	OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update smallstep/certificates to 0.29.0

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2025-12-03
OpenCVESSVC decisionnone—
CNACVSS 3.15read 2026-10-23
CNAweakness (CWE)CWE-863read 2026-10-23
FIRST EPSSEPSS score0.2 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:H
Published: 2025-12-03
Last Modified: 2026-10-18
NVD status: Deferred

Frequently asked questions

What is CVE-2025-66406?

Is CVE-2025-66406 actively exploited?

Active exploitation of CVE-2025-66406 has not been confirmed. Its EPSS score was 0.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-66406?

CVE-2025-66406 has a CVSS v3 base score of 5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:H.

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