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.
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].
Impact
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2026-30836 has a CVSS score of 10.0 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.30.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
In v0.30.0, additional validation was added to SCEP provisioners, so that they reject unsupported message types.
Frequently Asked Questions
- What is CVE-2026-30836? CVE-2026-30836 is a critical-severity improper authentication vulnerability in github.com/smallstep/certificates (go), affecting versions < 0.30.0. It is fixed in 0.30.0. The application does not adequately verify the identity of a user, device, or process before granting access.
- How severe is CVE-2026-30836? CVE-2026-30836 has a CVSS score of 10.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/smallstep/certificates are affected by CVE-2026-30836? github.com/smallstep/certificates (go) versions < 0.30.0 is affected.
- Is there a fix for CVE-2026-30836? Yes. CVE-2026-30836 is fixed in 0.30.0. Upgrade to this version or later.
- Is CVE-2026-30836 exploitable, and should I be worried? Whether CVE-2026-30836 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-30836 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-30836? Upgrade
github.com/smallstep/certificatesto 0.30.0 or later.