GHSA-9qq8-cgcv-qmc9
LOWGHSA-9qq8-cgcv-qmc9 is a low-severity (CVSS 3.7) CWE-129 vulnerability in github.com/smallstep/certificates. O3 Security confirms whether GHSA-9qq8-cgcv-qmc9 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Step CA affected by an index out of bounds panic in TPM attestation EKU validation
Blast Radius
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 trigger an index out-of-bounds panic in Step CA by sending a crafted attestation key (AK) certificate with an empty Extended Key Usage (EKU) extension during TPM device attestation.
Details
When processing a device-attest-01 ACME challenge using TPM attestation, Step CA validates that the AK certificate contains the tcg-kp-AIKCertificate Extended Key Usage OID. During this validation, the EKU extension value is decoded from its ASN.1 representation and the first element is checked. A crafted certificate could include an EKU extension that decodes to an empty sequence, causing the code to panic when accessing the first element of the empty slice.
This vulnerability is only reachable when a device-attest-01 ACME challenge with TPM attestation is configured. Deployments not using TPM device attestation are not affected.
Mitigations
If you are unable to upgrade to v0.30.0 or newer, the attack can be mitigated by disabling or removing any ACME provisioners that use TPM device attestation (device-attest-01).
Fix
In v0.30.0, a bounds check was added to validateAKCertificateExtendedKeyUsage so that an empty EKU sequence is treated as a validation failure rather than causing a panic.
Acknowledgements
This issue was identified and reported by @1seal (Oleh Konko).
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/smallstep/certificates | ≥ 0.24.0&&< 0.30.0 | 0.30.0 |
Detection & 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 GHSA-9qq8-cgcv-qmc9 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-9qq8-cgcv-qmc9 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-9qq8-cgcv-qmc9. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-9qq8-cgcv-qmc9 in your dependencies?
O3 detects GHSA-9qq8-cgcv-qmc9 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.