Reject malformed ECH outer extension references in crypto/tls

{
  "id": "26172798606cb3099328f6ab67b3a3873e33d260db356bd6cca6afdc5b92f66b",
  "url": "https://osv.dev/vulnerability/GO-2026-6607",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Reject malformed ECH outer extension references in crypto/tls",
    "summary": "Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and curb the memory amplification vector as a result.",
    "evidence": "osv:GO-2026-6607",
    "products": [
      {
        "name": {
          "value": "stdlib",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.26.9",
            "evidence": "/affected/0/ranges"
          },
          {
            "value": "1.27.2",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "GO-2026-6607",
      "aliases": [
        "BIT-golang-2026-97031",
        "CVE-2026-97031",
        "GO-2026-6607"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.26.9"
                },
                {
                  "introduced": "1.27.0-0"
                },
                {
                  "fixed": "1.27.2"
                }
              ]
            }
          ],
          "package": {
            "name": "stdlib",
            "purl": "pkg:golang/stdlib",
            "ecosystem": "Go"
          },
          "database_specific": {
            "source": "https://vuln.go.dev/ID/GO-2026-6607.json"
          },
          "ecosystem_specific": {
            "imports": [
              {
                "path": "crypto/tls",
                "symbols": [
                  "Conn.Handshake",
                  "Conn.HandshakeContext",
                  "Conn.Read",
                  "Conn.Write",
                  "Dial",
                  "DialWithDialer",
                  "Dialer.Dial",
                  "Dialer.DialContext",
                  "QUICConn.Start",
                  "decodeInnerClientHello"
                ]
              }
            ]
          }
        }
      ],
      "modified": "2026-10-16T09:55:33.249742867Z",
      "provider": "osv",
      "references": [
        "https://go.dev/cl/847312",
        "https://go.dev/issue/81855",
        "https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"
      ],
      "provider_metadata": {
        "url": "https://pkg.go.dev/vuln/GO-2026-6607",
        "review_status": "REVIEWED"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-97031",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 338676,
  "published_at": "2026-10-08T22:31:09+00:00"
}