CVE-2026-55166
Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acme_url without an effective server-side destination restriction and trigger AcmeHandler.setup_acme_client to make backend requests. An attacker could target cloud instance metadata or internal services from Lemur network context, potentially obtaining credentials available to the host.
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The advisory also identifies creator-equality authorization behavior that could preserve access to certificate key material after ownership or role changes, with insufficient export_private_key audit context to distinguish that access path. Together, the acme_url server-side request forgery and authorization weakness could expose cloud credentials and long-lived PKI private-key access. The fix adds ACME_DIRECTORY_HOST_ALLOWLIST validation and enriches key-export audit events with creator and current-owner context. This issue is fixed in version 1.9.2.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L
- Puntuación base: 9.9
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.29%
- Percentil entre todas las CVEs puntuadas: 19
- Fecha de la puntuación: 2/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement92 % - Impacto principal
T1552.005Cloud Instance Metadata APIcredential access90 % - Impacto secundario
T1090.001Internal Proxycommand and control85 % - Impacto secundario
T1212Exploitation for Credential Accesscredential access80 %
AV:N/PR:L permite T1210 (servicios remotos desde contexto autenticado). SSRF en acme_url expone credenciales cloud (T1552.005) y permite proxy interno (T1090.001). Acceso a material PKI tras cambios de rol revela debilidad de autorización (T1212).
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-285, CWE-639, CWE-918
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-55166",
"cveTags": [],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-55166",
"role": "CISA Coordinator",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"version": "2.0.3",
"timestamp": "2026-08-18T19:33:55.265998Z"
}
}
],
"cvssMetricV31": [
{
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"source": "security-advisories@github.com",
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"baseScore": 9.9,
"attackVector": "NETWORK",
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "LOW",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 6,
"exploitabilityScore": 3.1
}
]
},
"affected": [
{
"source": "security-advisories@github.com",
"affectedData": [
{
"vendor": "Netflix",
"product": "lemur",
"versions": [
{
"status": "affected",
"version": "< 1.9.2"
}
]
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],
"published": "2026-08-18T19:16:58.783",
"references": [
{
"url": "https://github.com/Netflix/lemur/commit/872f6e282542352f2bf3f6e2bcc504ab81e1843d",
"source": "security-advisories@github.com"
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{
"url": "https://github.com/Netflix/lemur/releases/tag/v1.9.2",
"source": "security-advisories@github.com"
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{
"url": "https://github.com/Netflix/lemur/security/advisories/GHSA-v2wp-frmc-5q3v",
"source": "security-advisories@github.com"
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{
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"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
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"description": [
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{
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"descriptions": [
{
"lang": "en",
"value": "Lemur manages TLS certificate creation. Prior to 1.9.2, authenticated users could influence an ACME authority acme_url without an effective server-side destination restriction and trigger AcmeHandler.setup_acme_client to make backend requests. An attacker could target cloud instance metadata or internal services from Lemur network context, potentially obtaining credentials available to the host. The advisory also identifies creator-equality authorization behavior that could preserve access to certificate key material after ownership or role changes, with insufficient export_private_key audit context to distinguish that access path. Together, the acme_url server-side request forgery and authorization weakness could expose cloud credentials and long-lived PKI private-key access. The fix adds ACME_DIRECTORY_HOST_ALLOWLIST validation and enriches key-export audit events with creator and current-owner context. This issue is fixed in version 1.9.2."
}
],
"lastModified": "2026-09-08T21:02:26.047",
"sourceIdentifier": "security-advisories@github.com"
}