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CVE-2026-75595

Full vulnerability record from the local CVENow database.

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.

Severity
CRITICAL
CVSS score
9.1 (v4.0)
Vulnerability status
Analyzed
Source identifier
[email protected]
Published
2026-08-19 21:17:37.563000
Last modified
2026-10-26 10:10:00.140000
View original CVE JSON 
{
  "id": "CVE-2026-75595",
  "sourceIdentifier": "[email protected]",
  "published": "2026-08-19T21:17:37.563",
  "lastModified": "2026-10-26T10:10:00.140",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
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      "lang": "en",
      "value": "Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final."
    },
    {
      "lang": "es",
      "value": "Netty es un framework de aplicación de red asíncrono y basado en eventos. Antes de las versiones 4.1.137.Final y 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode comprueba el desplazamiento incorrecto antes de leer la cabecera de handshake TLS de cuatro bytes, por lo que un ClientHello cuya cabecera de handshake abarca registros puede causar una IndexOutOfBoundsException e invocar select(ctx, null). Esto selecciona el SslContext predeterminado en lugar del contexto específico de SNI. En implementaciones donde clientAuth=REQUIRE por SNI es la única puerta de TLS mutuo, el SslContext predeterminado usa clientAuth=NONE o clientAuth=OPTIONAL, y no existe verificación de certificado a nivel de aplicación, un atacante remoto no autenticado puede eludir el requisito de TLS mutuo de la ruta protegida. Este problema está solucionado en las versiones 4.1.137.Final y 4.2.17.Final."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "netty",
          "product": "netty",
          "versions": [
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              "version": "< 4.1.137.Final",
              "status": "affected"
            },
            {
              "version": ">= 4.2.0.Final, < 4.2.17.Final",
              "status": "affected"
            }
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  "metrics": {
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          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "subAvailabilityImpact": "NONE",
          "exploitMaturity": "NOT_DEFINED",
          "confidentialityRequirement": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "valueDensity": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED"
        }
      }
    ],
    "cvssMetricV31": [
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        "type": "Primary",
        "cvssData": {
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          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "NONE"
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        "impactScore": 5.2
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    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-08-20T14:05:51.091097Z",
          "id": "CVE-2026-75595",
          "options": [
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              "exploitation": "none"
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          "role": "CISA Coordinator",
          "version": "2.0.3"
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  "weaknesses": [
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      "source": "[email protected]",
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      "description": [
        {
          "lang": "en",
          "value": "CWE-754"
        }
      ]
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
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              "matchCriteriaId": "C2D95C1D-B022-435F-B4C7-33FC460064EA"
            },
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  "references": [
    {
      "url": "https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7",
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    {
      "url": "https://github.com/netty/netty/security/advisories/GHSA-c4c3-7fpv-j4q5",
      "source": "[email protected]",
      "tags": [
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}