CVE-2026-40097
LowCVSS 3.7Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
Step CA from 0.24.0 to before 0.30.0-rc3 allows an attacker to trigger an index out-of-bounds panic by sending a crafted attestation key (AK) certificate with an empty Extended Key Usage extension during TPM device attestation. The vulnerability is only reachable when a device-attest-01 ACME challenge with TPM attestation is configured.
Risk Assessment
An attacker can remotely trigger a panic in the Step CA service, causing denial of service for certificate issuance processes. Deployments not using TPM device attestation are not affected.
Recommendation
Update Step CA to version 0.30.0-rc3 or later. If TPM attestation is not required, consider disabling the device-attest-01 challenge with TPM attestation.
Other vulnerabilities in Step CA
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS