{"cve":"CVE-2026-40097","nvd":{"published":"2026-04-10T17:17:12.823","modified":"2026-10-26T22:10:00.163","status":"Analyzed","description":"Step CA is an online certificate authority for secure, automated certificate management for DevOps. From 0.24.0 to before 0.30.0-rc3, 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. 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. This vulnerability is fixed in 0.30.0-rc3.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","score":3.7},"cwes":["CWE-129"],"references":["https://github.com/smallstep/certificates/commit/ffd31ac0a87e03b0224cb8363094bfe602242888","https://github.com/smallstep/certificates/pull/2569","https://github.com/smallstep/certificates/releases/tag/v0.30.0","https://github.com/smallstep/certificates/security/advisories/GHSA-9qq8-cgcv-qmc9"],"products":["smallstep:step-ca"],"source":"nvd","synced_at":"2026-10-26T22:26:44.656832877+00:00"},"epss":{"cve":"CVE-2026-40097","score":0.00181,"percentile":0.07613,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-9qq8-cgcv-qmc9","url":"https://osv.dev/vulnerability/GHSA-9qq8-cgcv-qmc9","summary":"Step CA affected by an index out of bounds panic in TPM attestation EKU validation","modified":"2026-06-25T19:56:06.351112363Z","packages":[{"ecosystem":"Go","name":"github.com/smallstep/certificates","purl":"pkg:golang/github.com/smallstep/certificates","ranges":[">=0.24.0 <0.30.0"],"fixed":["0.30.0"]}]},{"id":"GO-2026-5297","url":"https://osv.dev/vulnerability/GO-2026-5297","summary":"Step CA affected by an index out of bounds panic in TPM attestation EKU validation in github.com/smallstep/certificates","modified":"2026-06-25T19:45:30.538136207Z","packages":[{"ecosystem":"Go","name":"github.com/smallstep/certificates","purl":"pkg:golang/github.com/smallstep/certificates","ranges":[">=0.24.0 <0.30.0"],"fixed":["0.30.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}