CVE-2026-40097

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{"affected": [{"affectedData": [{"product": "certificates", "vendor": "smallstep", "versions": [{"status": "affected", "version": ">= 0.24.0, < 0.30.0-rc3"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:smallstep:step-ca:*:*:*:*:*:go:*:*", "matchCriteriaId": "ABA8B83F-37DD-4755-AFB6-CD76AF8A4F4A", "versionEndExcluding": "0.30.0", "versionStartIncluding": "0.24.0", "vulnerable": true}, {"criteria": "cpe:2.3:a:smallstep:step-ca:0.30.0:rc1:*:*:*:go:*:*", "matchCriteriaId": "D49EF50A-2928-4577-A5AD-0CD81C9E1AE8", "vulnerable": true}, {"criteria": "cpe:2.3:a:smallstep:step-ca:0.30.0:rc2:*:*:*:go:*:*", "matchCriteriaId": "E238C89C-4A97-4FA1-8DE0-9FE51CDF59B9", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Step CA es una autoridad de certificaci\u00f3n en l\u00ednea para la gesti\u00f3n segura y automatizada de certificados para DevOps. Desde la versi\u00f3n 0.24.0 hasta antes de la 0.30.0-rc3, un atacante puede desencadenar un p\u00e1nico por \u00edndice fuera de l\u00edmites en Step CA al enviar un certificado de clave de atestaci\u00f3n (AK) manipulado con una extensi\u00f3n de Uso Extendido de Clave (EKU) vac\u00eda durante la atestaci\u00f3n de dispositivo TPM. Al procesar un desaf\u00edo ACME device-attest-01 utilizando la atestaci\u00f3n TPM, Step CA valida que el certificado AK contenga el OID de Uso Extendido de Clave tcg-kp-AIKCertificate. Durante esta validaci\u00f3n, el valor de la extensi\u00f3n EKU se decodifica de su representaci\u00f3n ASN.1 y se verifica el primer elemento. Un certificado manipulado podr\u00eda incluir una extensi\u00f3n EKU que se decodifica a una secuencia vac\u00eda, causando que el c\u00f3digo entre en p\u00e1nico al acceder al primer elemento del slice vac\u00edo. Esta vulnerabilidad solo es alcanzable cuando se configura un desaf\u00edo ACME device-attest-01 con atestaci\u00f3n TPM. Las implementaciones que no utilizan la atestaci\u00f3n de dispositivo TPM no se ven afectadas. Esta vulnerabilidad est\u00e1 corregida en la versi\u00f3n 0.30.0-rc3."}], "id": "CVE-2026-40097", "lastModified": "2026-10-26T22:10:00.163", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40097", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-10T18:30:05.878982Z", "version": "2.0.3"}}]}, "published": "2026-04-10T17:17:12.823", "references": [{"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/smallstep/certificates/commit/ffd31ac0a87e03b0224cb8363094bfe602242888"}, {"source": "security-advisories@github.com", "tags": ["Issue Tracking", "Patch"], "url": "https://github.com/smallstep/certificates/pull/2569"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/smallstep/certificates/releases/tag/v0.30.0"}, {"source": "security-advisories@github.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://github.com/smallstep/certificates/security/advisories/GHSA-9qq8-cgcv-qmc9"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-129"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0.24.0,0.30.0-rc3)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "certificates", "source": "cna", "vendor": "smallstep"}, "product": "certificates", "vendor": "smallstep"}], "analysis": {"en": {"generated_at": "2026-04-10T18:23:31.136928+00:00", "value": {"mitigation_remediation": ["Upgrade smallstep certificates to 0.30.0-rc3 or later.", "If an upgrade is not immediately feasible, disable TPM device attestation in the device\u2011attest\u201101 ACME challenge configuration to exclude the vulnerable path.", "Monitor the CA logs for repeated panic or crash events related to TPM attestation as an early indicator of attempted exploitation."], "summary": {"action": "Immediate Patch", "impact": "Denial of Service via index out-of-bounds panic during TPM attestation"}, "threat_synthesis": {"affected_systems": "Affected deployments run smallstep certificates versions 0.24.0 through the last release before 0.30.0\u2011rc3 and only if the device\u2011attest\u201101 ACME challenge is configured to use TPM attestation. Systems that do not employ TPM attestation are not impacted.", "description_and_impact": "Step CA, an online certificate authority, contains a vulnerability that permits a crafted attestation key certificate with an empty Extended Key Usage extension to trigger an index out\u2011of\u2011bounds panic during TPM device attestation. The panic occurs when the code decodes the EKU ASN.1 value and attempts to access the first element of an empty sequence. This flaw is classified as CWE\u2011129 and results in an application crash, denying certificate issuance services to clients that trigger the attack. The impact is limited to service disruption rather than data theft.", "risk_and_exploitability": "The CVSS score of 3.7 reflects a low to medium severity focus on denial of service. No EPSS score is available, and the vulnerability is not listed in CISA KEV, indicating no publicly known exploits yet. The attack vector is inferred to be internal or privileged, requiring the ability to supply a crafted AK certificate during a TPM attestation challenge. The fix implemented in 0.30.0\u2011rc3 removes the bounds check flaw. As the condition is limited to a specific configuration, the likelihood of exploitation without this configuration is very low. Nevertheless, an attacker with access to the attestation path can deliberately disrupt service by repeatedly sending crafted certificates."}}}}, "created": "2026-04-13T12:43:53.399915+00:00", "updated": "2026-04-13T13:00:21.053940+00:00", "vendors": ["smallstep", "smallstep$PRODUCT$certificates"]}