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The Quasar CLI development server contains a critical vulnerability in its error-handling pipeline during Server-Side Rendering (SSR) and Static Site Generation (SSG) dev builds. When an application error occurs during rendering, the `renderSSRError()` function in `@quasar/render-ssr-error` catches the exception and constructs a custom HTTP 500 error page. To assist developers during debugging, this component extracts diagnostic environment state via getEnv(), collecting all system environment variables (process.env), incoming HTTP request headers, and client cookies.
Because Quasar CLI explicitly overrides Vite’s default `localhost` binding behavior to bind to 0.0.0.0, the dev server listens on all available network interfaces by default. Any unauthenticated network peer on the local network segment, container mesh, or shared host environment can issue a standard HTTP GET request to trigger or view an error page. This directly exposes critical system secrets, including cloud credentials, API keys, database connection strings, and access tokens stored in process.env.
Additionally, the error handler inserts this diagnostic dataset into an inline JavaScript object literal inside a `). However, standard HTML parsing rules process script end tags in a case-insensitive manner and tolerate trailing whitespace or slashes before the closing angle bracket. Because `.replaceAll()` uses an exact string match, alternative variants such as </SCRIPT>, </script >, or `` bypass the replacement. When arbitrary user-controlled inputs (such as incoming HTTP request headers or cookies decoded via decodeURIComponent) contain these variants, an attacker can prematurely close the script element and inject arbitrary markup or script tags.
DailyCVE Form:
Platform: Quasar CLI
Version: <2.2.4
Vulnerability: Info Leak & XSS
Severity: Critical
date: 2026-10-06
Prediction: Patch Released
What Undercode Say: Analytics
Bash Commands and Diagnostic Code
Check installed package version for @quasar/render-ssr-error npm list @quasar/render-ssr-error Verify if local dev server is listening on all interfaces (0.0.0.0) netstat -tuln | grep 3200
// Source pattern: Inadequate string replacement guard
// utils/render-ssr-error/src/index.js
const errorHtml = before +
JSON.stringify(data).replaceAll('</script>', String.raw<code><\/script></code>) +
after;
// Remediation pattern using case-insensitive regex or safe serialization
const safeHtml = before +
String(JSON.stringify(data)).replaceAll(new RegExp('</script', 'gi'), '<\/script') +
after;
How Exploit Mechanics Work
The exposure mechanics rely on two key flaws:
1. Unauthenticated Network Reachability: The dev server default host configuration overrides local loopback restrictions, allowing any TCP peer capable of routing to the host port to fetch the rendered error document and inspect the embedded JSON data structures.
2. Parser Context Breakout: HTML raw text parsing terminates `` passes through exact-match string replacements, the literal output breaks out of the JS string context into the HTML parser tree.
Protection
Update Dependencies: Upgrade `@quasar/render-ssr-error` to version `2.2.4` or higher, and `@quasar/app-vite` to version `3.3.0` or higher.
Bind Dev Server to Localhost: Explicitly set `devServer.host` to `127.0.0.1` or `localhost` inside `quasar.config.js` to prevent binding to 0.0.0.0.
Sanitize Output: Use robust JSON serialization libraries (such as serialize-javascript) that automatically escape HTML-sensitive characters (<, >, /) when embedding data into inline script tags.
Filter Environment Variables: Avoid dumping entire `process.env` objects into response payloads, redacting sensitive tokens and internal keys from diagnostic views.
Impact
Exposure of developer machine environment variables (AWS keys, npm tokens, database credentials), request headers, and session cookies to unauthorized network peers. Secondary impact includes potential cross-site script execution within the developer's origin context via payload injection into request attributes or cookies.
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Sources:
Reported By: github.com
Extra Source Hub:
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