CVE-2026-30836 is a critical-severity (CVSS 10) Improper Authentication vulnerability in github.com/smallstep/certificates. A fix is available for github.com/smallstep/certificates — see the affected versions and patch details below.
Step CA: Unauthenticated Certificate Issuance via SCEP UpdateReq (MessageType=18)
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-30836.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/smallstep/certificatesReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
An attacker can force a Step CA SCEP provisioner to create certificates without completing certain protocol authorization checks.
Details
SCEP requests carry a message type. On receipt of a SCEP request, Step CA starts processing it by parsing its contents. Message types that were considered valid, but not explicitly supported in Step CA, would result in getting parsed successfully. While processing the parsed SCEP message, authorization logic would be skipped for the non-supported message types.
As a result, the request would be treated as authorized, bypassing the authorization checks normally enforced as part of the SCEP protocol and its implementation in Step CA.
Authorization webhooks and regular CA policies, such as allowed names and restrictions on certificate validity periods, remain in place.
Mitigations
If you are unable to upgrade to v0.30.0 or newer, the attack can be mitigated by (temporarily) disabling or removing SCEP provisioners, or restricting access to SCEP provisioners to trusted clients only.
Fix
In v0.30.0, additional validation was added to SCEP provisioners, so that they reject unsupported message types.
Acknowledgements
This issue was identified and reported by Prasanth Sundararajan.
Embargo List
If your organization runs Step CA in production and would like advance, embargoed notification of future security updates, visit https://u.step.sm/disclosure to request inclusion on our embargo list.
Stay safe, and thank you for helping us keep the ecosystem secure.
If you have urgent questions, please contact [email protected].
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/smallstep/certificates | all versions | 0.30.0go get github.com/smallstep/certificates@v0.30.0 |
Affected Products
step-casmallstepDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/smallstep/certificates, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/smallstep/certificates to 0.30.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30836 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-30836 in your dependencies?
Find it across Go, including transitive dependencies.