Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS

{
  "id": "0dbba7d58a001e1917ce63b81930dcf97879987f1ffc69cb8215fb62ffe625ee",
  "url": "https://osv.dev/vulnerability/CVE-2026-100662",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS",
    "summary": "Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain an uncontrolled resource consumption vulnerability in the QPACK encoder-stream instruction decoder (QpackEncoderHandler, installed on the peer-initiated unidirectional QPACK encoder stream, type 0x02). The handler accepts an attacker-declared string-literal length of up to Integer.MAX_VALUE (~2 GiB) for the Name Length and Value Length fields of the \"Insert With Literal Name\" instruction (RFC 9204 §4.3.3), with no per-instruction or per-literal length cap and no cumulation-size limit; the existing HTTP/3 limits (maxHeaderListSize, maxUnknownFramePayloadLength, DEFAULT_MAX_FIELD_SECTION_SIZE) are not applied to this handler. A remote, unauthenticated peer with an established HTTP/3 connection to a default Netty HTTP/3 server can declare a very large literal length and then trickle fewer bytes than declared, causing the ByteToMessageDecoder MERGE cumulator to retain and grow the per-connection buffer, and ultimately triggering a large byte-array allocation. This leads to unbounded per-connection heap growth and OutOfMemoryError, resulting in denial of service. Fixed in 4.2.18.Final.",
    "evidence": "osv:CVE-2026-100662",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-100662",
      "aliases": [
        "CVE-2026-100662",
        "GHSA-f64r-x647-cg8w"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/netty/netty",
              "type": "GIT",
              "events": [
                {
                  "introduced": "09e64d259c99be8b5b2a471a78f11e65eb82598a"
                },
                {
                  "fixed": "2521f494432e27415a567d3a81a9eb907abf20b3"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "4.2.0.Final"
                      },
                      {
                        "fixed": "4.2.18.Final"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
            "netty-clang-bin",
            "netty-4.2.17.Final",
            "netty-4.2.16.Final",
            "netty-4.2.15.Final",
            "netty-4.2.14.Final",
            "netty-4.2.13.Final",
            "netty-4.2.12.Final",
            "netty-4.2.11.Final",
            "netty-4.2.10.Final",
            "netty-4.2.9.Final",
            "netty-4.2.8.Final",
            "netty-4.2.7.Final",
            "netty-4.2.6.Final",
            "netty-4.2.5.Final",
            "netty-4.2.4.Final",
            "netty-4.2.3.Final",
            "netty-4.2.2.Final",
            "netty-4.2.1.Final",
            "netty-4.2.0.Final"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-100662.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.349664399Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100662.json",
        "https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-100662",
        "https://www.vulncheck.com/advisories/netty-http-3-qpack-encoder-stream-unbounded-memory-exhaustion-dos"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100662.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-100662",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509936,
  "published_at": "2026-09-26T13:23:28.99+00:00"
}