EUVD-2026-21506
GHSA-9qq8-cgcv-qmc9
CVSS Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Lifecycle Timeline
4Description
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.
Analysis
Step CA versions 0.24.0 through 0.30.0-rc2 suffer a denial-of-service vulnerability where an attacker can trigger an index out-of-bounds panic by sending a crafted TPM attestation key certificate with an empty Extended Key Usage extension during device-attest-01 ACME challenges. The vulnerability affects only deployments that have explicitly configured TPM device attestation; organizations using Step CA for standard certificate management are unaffected. …
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