René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Error on Socket unref: Cannot read properties of undefined (reading 'Symbol(timeout)')","articleBody":"### Version\n\nv24.18.0\n\n### Platform\n\n```text\nLinux scatha 7.0.11-76070011-generic #202606011647~1780583630~22.04~70ad774 SMP PREEMPT_DYNAMIC Thu J x86_64 x86_64 x86_64 GNU/Linux\n```\n\n### Subsystem\n\nlib/internal/tls/wrap.js\n\n### What steps will reproduce the bug?\n\nVery minimal (and artificial):\n\n```js\nconst net = require('net');\nconst s = new net.Socket();\ns._parent = undefined; // a chain link left `undefined` (see note on the trigger)\ns._unrefTimer();\n```\n\nMore representative, though the real case involved some library setting the handle to `undefined` whereas this does it explicitly:\n\n```js\nconst fs = require('fs');\nconst tls = require('tls');\n\n// self-signed cert: openssl req -x509 -newkey rsa:2048 -nodes \\\n//   -keyout key.pem -out cert.pem -days 2 -subj \"/CN=localhost\"\nconst opts = { key: fs.readFileSync('key.pem'), cert: fs.readFileSync('cert.pem') };\n\nconst server = tls.createServer(opts, (conn) => {\n  setTimeout(() => conn.write('x'), 50); // inbound record after the chain is corrupted\n});\n\nserver.listen(0, () => {\n  const client = tls.connect(\n    { port: server.address().port, rejectUnauthorized: false },\n    () => { client._parent = undefined; }, // invariant violation (stands in for teardown race)\n  );\n  client.on('error', () => {});\n});\n```\n\n### How often does it reproduce? Is there a required condition?\n\nIt seems to happen very sporadically; we're seeing a few instances a day in a system that handles significant volume.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nThe object should be unref-ed, and with no parent, the parent traversal should be a no-op.\n\n### What do you see instead?\n\n```\nTypeError: Cannot read properties of undefined (reading 'Symbol(timeout)')\n    at TLSSocket._unrefTimer (node:net:529:10)\n    at TLSWrap.onStreamRead (node:internal/stream_base_commons:172:23)\n```\n\n### Additional information\n\nIn `lib/net.js`, the parent chain is traversed with an exact equality check `s !== null` which fails if some library happens to null out the parent ref with `undefined`, instead. If this were a lax (`s != null`) check, the error ought to go away.\n\n```js\n  const { kTimeout } = require('internal/timers');   // kTimeout = Symbol('timeout')\n\n  Socket.prototype._unrefTimer = function _unrefTimer() {\n    for (let s = this; s !== null; s = s._parent) {\n      if (s[kTimeout])\n        s[kTimeout].refresh();\n    }\n  };\n```","author":{"url":"https://github.com/haggholm","@type":"Person","name":"haggholm"},"datePublished":"2026-07-14T04:59:16Z","url":"https://github.com/nodejs/node/issues/64490"}