CVE-2026-40097: Step CA is an online certificate authority for secure, automated certificate management for DevOps

Routine

LOW 3.7REMOTEUPGRADE

CVE-2026-40097 is a low-severity flaw (CVSS 3.7) affecting step-ca. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 con

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 92%)
CISA exploited list	No
Weakness	CWE-129
Published	2026-04-10
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: smallstep

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-10 17:17 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

smallstep step-ca UPGRADE

Affected: >= 0.24.0 and < 0.30.0 · 0.30.0 rc1 · 0.30.0 rc2

Fixed in: 0.30.0

Safe to downgrade to: a release before 0.24.0

1. Check installed version

apt-cache policy step-ca || rpm -q step-ca || step-ca --version

2. UPGRADE to 0.30.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade step-ca

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade step-ca

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.24.0 (Debian / Ubuntu)

apt-cache madison step-ca sudo apt install step-ca=<VERSION_BEFORE_0.24.0> sudo apt-mark hold step-ca

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list step-ca sudo dnf downgrade step-ca-<VERSION_BEFORE_0.24.0> sudo dnf versionlock add step-ca

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40097?

step-ca: upgrade to 0.30.0. Exact commands for each OS are on this page.

Is CVE-2026-40097 being exploited?

CVE-2026-40097 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40097 affect?

CVE-2026-40097 affects step-ca. Severity is low (CVSS 3.7). 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)

How urgent is CVE-2026-40097?

Priority 20/100. Remotely exploitable, no login, no user action

References

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