CVE-2026-92395
@fastify/proxy-addr is a Fastify plugin that determines a request's client address behind trusted reverse proxies, and it backs Fastify request.ip and request.ips. In versions 3.0.0 through 5.1.0, a trust subnet written in IPv4-mapped IPv6 notation with an IPv4-sized prefix, such as ::ffff:10.0.0.0/8 instead of the correct ::ffff:10.0.0.0/104, is accepted without error but trusts every IPv4 address on the internet rather than the block it names.
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Because the socket peer then becomes trusted at hop 0, any unauthenticated client can supply an arbitrary X-Forwarded-For header and control the address the application reads, which defeats IP-based access control, rate limiting, geolocation, and audit logging. The plugin inherited this defect from the upstream proxy-addr module (CVE-2026-90711). The issue is fixed in @fastify/proxy-addr 5.1.1, and users should upgrade to 5.1.1 or later. As a workaround, ensure any IPv4-mapped IPv6 trust subnet uses a prefix length of at least 97, or express the range in plain IPv4 notation.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- Puntuación base: 9.1
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.33%
- Percentil entre todas las CVEs puntuadas: 24
- Fecha de la puntuación: 6/10/2026
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
T1190Exploit Public-Facing Applicationinitial access85 % - Impacto principal
T1078Valid Accountsstealth · persistence · privilege escalation · initial access90 % - Impacto secundario
T1005Data from Local Systemcollection75 % - Impacto secundario
T1583.006Web Servicesresource development70 %
Vulnerabilidad en validación de subredes IPv6 (CWE-290) en plugin Fastify expuesto en red (AV:N, PR:N). Permitiendo falsificar X-Forwarded-For (T1078) y eludir controles de IP. Alto impacto de confidencialidad (C:H) sugiere acceso a datos sin autenticación. Afecta auditoría y geolocalización (T1005,
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-290, CWE-348, CWE-697
Referencias
JSON original (NVD)
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"id": "CVE-2026-92395",
"role": "CISA Coordinator",
"options": [
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"exploitation": "none"
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"automatable": "yes"
},
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"version": "2.0.3",
"timestamp": "2026-09-17T18:38:56.138579Z"
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"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "NONE",
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"affected": [
{
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"affectedData": [
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"vendor": "@fastify/proxy-addr",
"product": "@fastify/proxy-addr",
"versions": [
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"status": "affected",
"version": "3.0.0",
"lessThan": "5.1.1",
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"published": "2026-09-16T15:19:01.857",
"references": [
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"url": "https://cna.openjsf.org/security-advisories.html",
"source": "ce714d77-add3-4f53-aff5-83d477b104bb"
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"description": [
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"descriptions": [
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"value": "@fastify/proxy-addr is a Fastify plugin that determines a request's client address behind trusted reverse proxies, and it backs Fastify request.ip and request.ips. In versions 3.0.0 through 5.1.0, a trust subnet written in IPv4-mapped IPv6 notation with an IPv4-sized prefix, such as ::ffff:10.0.0.0/8 instead of the correct ::ffff:10.0.0.0/104, is accepted without error but trusts every IPv4 address on the internet rather than the block it names. Because the socket peer then becomes trusted at hop 0, any unauthenticated client can supply an arbitrary X-Forwarded-For header and control the address the application reads, which defeats IP-based access control, rate limiting, geolocation, and audit logging. The plugin inherited this defect from the upstream proxy-addr module (CVE-2026-90711). The issue is fixed in @fastify/proxy-addr 5.1.1, and users should upgrade to 5.1.1 or later. As a workaround, ensure any IPv4-mapped IPv6 trust subnet uses a prefix length of at least 97, or express the range in plain IPv4 notation."
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"lastModified": "2026-09-17T19:17:07.053",
"sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb"
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