high · 8.7 Patched

Qwik: Crashing any Qwik Server via Resource thenable

CVE-2026-84994 · GHSA-x586-xvc8-g7q6 · published 15 Oct 2026

How serious is it

  • Severity: high, CVSS score 8.7 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-84994?

Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.

Who is affected

  • @builder.io/qwik (npm) < 1.20.0
  • @qwik.dev/core (npm) < 2.0.0-beta37

How to check

  1. Run npm ls @builder.io/qwik in your project to see the installed version, including copies pulled in by other packages.
  2. Run npm ls @qwik.dev/core in your project to see the installed version, including copies pulled in by other packages.
  3. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.
  4. Or run npx shippable-dev scan localhost:3000 in your project folder. It reads your lockfile and flags this vulnerability along with every other known one.

How to fix

Copies a prompt for Claude Code, Cursor or Codex: it checks your lockfiles for this and upgrades it.
  1. On < 1.20.0: Upgrade @builder.io/qwik to 1.20.0 or later, commit the lockfile and redeploy.
  2. On < 2.0.0-beta37: Upgrade @qwik.dev/core to 2.0.0-beta37 or later, commit the lockfile and redeploy.
  3. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

### Summary A Qwik server in the default configuration can be crashed with one unauthenticated HTTP request. During qwik-json body parsing, `ResourceSerializer.$fill$` does `Promise.resolve(resource._resolved)`. If `_resolved` is a plain object whose `.then` is a QRL for an unregistered symbol, the async QRL rejects, the rejection is orphaned, and Node terminates the process via its default unhandled-rejection policy. ### Impact One unauthenticated request crashes the server. Looping keeps every replica dead as long as the attacker sends requests.

Check your whole app

Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.

References

Merged from GitHub Advisory Database. Last updated 23 Oct 2026. All vulnerabilities · RSS · JSON

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