CVE-2026-84994 Qwik: Crashing any Qwik Server via Resource thenable
An unauthenticated attacker can crash a Qwik server by sending a crafted request that triggers an unhandled promise rejection, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-84994?
CVE-2026-84994 is a high-severity denial of service vulnerability in @builder.io qwik, published on 13 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Qwik is a performance-focused JavaScript framework. Prior to @builder.io/qwik 1.20.0 and @qwik.dev/core 2.0.0-beta.37, default server-side qwik-json deserialization causes ResourceSerializer.$fill$ to pass resource._resolved to Promise.resolve without first rejecting attacker-controlled thenables. An unauthenticated request can provide a plain object whose then property is a QRL for an unregistered symbol, causing an orphaned asynchronous rejection that terminates Node.js under its default unhandled-rejection policy. A single request can crash a server, and repeated requests can keep replicas unavailable. This issue is fixed in @builder.io/qwik 1.20.0 and @qwik.dev/core 2.0.0-beta.37.
Weakness: CWE-248
Which versions are affected by CVE-2026-84994?
4 open source packages ship an affected version, including @builder.io/qwik and @qwik.dev/core.
| Package | Affected | Fixed in |
|---|---|---|
@builder.io/qwik npm | All versions | 1.20.0 |
@builder.io/qwik npm | All versions | 1.20.0 |
@qwik.dev/core npm | All versions | 2.0.0-beta37 |
@qwik.dev/core npm | All versions | 2.0.0-beta37 |
How do I fix CVE-2026-84994?
Upgrade @builder.io/qwik to 1.20.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-84994 being exploited?
There is no known exploitation of CVE-2026-84994 in the wild and no public exploit code.
Sources
Also known as GHSA-x586-xvc8-g7q6.