PT-2026-31991 · Step Ca · Step Ca

1Seal · Published 2026-04-10 · Updated 2026-04-28 · CVE-2026-40097

Positive Technologies (AI Summary)

CVSS v3.1

3.7

Low

Base vector

AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

Name of the Vulnerable Software and Affected Versions Step CA versions 0.24.0 through 0.30.0-rc3

Description 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. During TPM device attestation, Step CA validates that the AK certificate contains the tcg-kp-AIKCertificate Extended Key Usage OID. 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.

Recommendations Upgrade to version 0.30.0-rc3 or newer. If unable to upgrade, disable or remove any ACME provisioners that use TPM device attestation (device-attest-01).

Fix

Improper Validation of Array Index

Weakness Enumeration

CWE-129

Related Identifiers

CVE-2026-40097

GHSA-9QQ8-CGCV-QMC9

Affected Products

Step Ca

References · 10

• https://github.com/smallstep/certificates/commit/ffd31ac0a87e03b0224cb8363094bfe602242888 · Patch
• https://github.com/smallstep/certificates/security/advisories/GHSA-9qq8-cgcv-qmc9 · Vendor Advisory
• https://github.com/smallstep/certificates/pull/2569 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-40097 · Security Note
• https://osv.dev/vulnerability/GHSA-9qq8-cgcv-qmc9 · Vendor Advisory
• https://github.com/smallstep/certificates/releases/tag/v0.30.0 · Note
• https://github.com/smallstep/certificates · Note
• https://twitter.com/dailycve/status/2043024878786212096 · Twitter Post
• https://twitter.com/CVEnew/status/2042710228995563716 · Twitter Post
• https://twitter.com/_cvereports/status/2049068790789419297 · Twitter Post