CVE-2021-43808

Laravel Framework XSS in Blade templating engine

@section('content')
<input value="{{ $value }}">
@show

@extends('parent')

@section('content')
<input value="{{ $value }}">
@endsection

Route::get('/example', function() {
    $value = '//localhost/###parent-placeholder-040f06fd774092478d450774f5ba30c5da78acc8## onclick=location.assign(this.value);//';

    return view('child', ['value' => $value]);
});

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2021-43808 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.20.42, 7.30.6, 8.75.0); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2021-43808? CVE-2021-43808 is a medium-severity cross-site scripting (XSS) vulnerability in laravel/framework (composer), affecting versions < 6.20.42. It is fixed in 6.20.42, 7.30.6, 8.75.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2021-43808? CVE-2021-43808 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2021-43808?
   • laravel/framework (composer) (versions < 6.20.42)
   • illuminate/view (composer) (versions < 6.20.42)
4. Is there a fix for CVE-2021-43808? Yes. CVE-2021-43808 is fixed in 6.20.42, 7.30.6, 8.75.0. Upgrade to this version or later.
5. Is CVE-2021-43808 exploitable, and should I be worried? Whether CVE-2021-43808 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-43808 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-43808?
   • Upgrade laravel/framework to 6.20.42 or later
   • Upgrade laravel/framework to 7.30.6 or later
   • Upgrade laravel/framework to 8.75.0 or later
   • Upgrade illuminate/view to 6.20.42 or later
   • Upgrade illuminate/view to 7.30.6 or later
   • Upgrade illuminate/view to 8.75.0 or later

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