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Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

Type: advisorySources: OSV

Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-45416
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 03:06 UTC · Revision 1

Source evidence

Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

core-osv · Original source

Published 12 Jun 2026, 14:10 UTC

Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

osv:CVE-2026-45416
Complete source record
{
  "id": "9dd2917450b8e379749abb12e331317bb60116b9ff79de7937c5873121a40237",
  "url": "https://osv.dev/vulnerability/CVE-2026-45416",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes",
    "summary": "Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes. Versions 4.1.135.Final and 4.2.15.Final patch the issue.",
    "evidence": "osv:CVE-2026-45416",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-45416",
      "aliases": [
        "CVE-2026-45416",
        "GHSA-x4gw-5cx5-pgmh"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/netty/netty",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "f05f765d81460799c53123a207f665bf3b465171"
                },
                {
                  "introduced": "09e64d259c99be8b5b2a471a78f11e65eb82598a"
                },
                {
                  "fixed": "a41f7b289ce1d697c50846f3ade3983e22b2ed40"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.1.135"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "4.2.0"
                      },
                      {
                        "fixed": "4.2.15"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f05f765d81460799c53123a207f665bf3b465171"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "netty-4.1.135.Final"
                  },
                  {
                    "range": [
                      {
                        "fixed": "a41f7b289ce1d697c50846f3ade3983e22b2ed40"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "netty-4.2.15.Final"
                  }
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45416.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.062524248Z",
      "provider": "osv",
      "references": [
        "https://github.com/netty/netty/releases/tag/netty-4.1.135.Final",
        "https://github.com/netty/netty/releases/tag/netty-4.2.15.Final",
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45416.json",
        "https://access.redhat.com/errata/RHSA-2026:26017",
        "https://access.redhat.com/errata/RHSA-2026:26018",
        "https://access.redhat.com/errata/RHSA-2026:26586",
        "https://access.redhat.com/errata/RHSA-2026:28573",
        "https://access.redhat.com/errata/RHSA-2026:34608",
        "https://access.redhat.com/errata/RHSA-2026:37390",
        "https://access.redhat.com/errata/RHSA-2026:41951",
        "https://access.redhat.com/errata/RHSA-2026:48151",
        "https://access.redhat.com/errata/RHSA-2026:49700",
        "https://access.redhat.com/errata/RHSA-2026:49701",
        "https://access.redhat.com/errata/RHSA-2026:50085",
        "https://access.redhat.com/errata/RHSA-2026:53644",
        "https://access.redhat.com/errata/RHSA-2026:53645",
        "https://access.redhat.com/errata/RHSA-2026:53646",
        "https://access.redhat.com/errata/RHSA-2026:54435",
        "https://access.redhat.com/errata/RHSA-2026:62260",
        "https://access.redhat.com/errata/RHSA-2026:65126",
        "https://access.redhat.com/errata/RHSA-2026:66488",
        "https://access.redhat.com/errata/RHSA-2026:66545",
        "https://access.redhat.com/security/cve/CVE-2026-45416",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45416.json",
        "https://github.com/netty/netty/security/advisories/GHSA-x4gw-5cx5-pgmh",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45416",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2488391"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45416.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-45416",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 499900,
  "published_at": "2026-06-12T14:10:05.585+00:00"
}