Overview
The password-reset flow in Laravel 5.4.x could be abused when generating the reset URL, enabling phishing scenarios where users are directed to attacker-controlled hosts. CVE-2017-9303 describes a case where Laravel 5.4.x before 5.4.22 did not properly constrain the host portion of the password-reset URL, making it easier for an attacker to craft a phishing link that users might trust. This is tied to CWE-20 (Improper Input Validation) because the host part of the URL was not properly validated or restricted when constructing the reset link, leading to a trust boundary violation in email-delivered reset URLs. In practice, an adversary could influence the host via misconfigurations or request headers, resulting in a reset link that points to a domain under the attacker’s control.
In real-world exploitation, an attacker could craft an email that included a password reset URL pointing to a domain they own. If a user clicked the link, they would be taken to a phishing page controlled by the attacker rather than the legitimate application, potentially enabling credential theft or other social engineering. The mitigation requires ensuring the host portion of reset URLs is canonical and derived from the application’s trusted configuration rather than the request or an unvalidated host value. Upgrading to the patched Laravel release (5.4.22 or later) is the primary defense, complemented by explicit host canonicalization and verification in URL generation.
Remediation focuses on both version upgrade and code-level hardening. After upgrading, ensure that all password-reset URL generation uses a canonical host sourced from config('app.url') (or an equivalent trusted source) and not from the incoming request. Add tests that exercise URL generation with different hosts to verify the host is always the canonical one. Finally, audit any custom mailers or password-reset utilities to ensure they do not bypass canonical host handling.
This guide provides concrete code changes and a before/after pattern you can adapt in your Laravel project.
Affected Versions
5.4.x before 5.4.22 (5.4.0 - 5.4.21)
Code Fix Example
Laravel API Security Remediation
<?php
// Vulnerable pattern: reset URL derived from the current request host
function buildResetUrlVulnerable($token) {
// This uses the request-derived host and can be spoofed
return url('/password/reset/'.$token);
}
// Fixed pattern: build URL using canonical host from app config
function buildResetUrlFixed($token) {
$appUrl = rtrim(config('app.url'), '/');
return $appUrl.'/password/reset/'.$token;
}
// Example usage
$token = 'ABC123';
echo '[VULNERABLE] '.buildResetUrlVulnerable($token)."\n";
echo '[FIXED] '.buildResetUrlFixed($token)."\n";
?>