Overview
The CVE-2017-14775 reference highlights a token verification weakness in Laravel where the remember_me token verification could be subverted due to a non-constant-time comparison in DatabaseUserProvider. While this CVE focuses on authentication token handling (CWE-200), the underlying lesson is the risk of handling untrusted input and performing security-sensitive comparisons without proper defensive coding. SSRF-like issues arise when an application accepts untrusted input to fetch remote resources, potentially enabling internal network access, data leakage, or RCE paths if the fetch logic interacts with internal services or restricted endpoints. This guide adapts the broader principle-validate and tightly control untrusted inputs and comparison logic-to SSRF mitigation in modern Laravel applications.
Affected Versions
Laravel < 5.5.10
Code Fix Example
Laravel API Security Remediation
// Vulnerable pattern (SSR F risk in Laravel) - fetches arbitrary remote content based on user input
<?php
$url = $_GET['url'];
$contents = file_get_contents($url);
echo $contents;
?>
// Fixed pattern - validate, restrict to allowlisted hosts, and block private/internal IPs before fetching
<?php
use Illuminate\\Support\\Facades\\Http;
$url = $_GET['url'];
// Basic URL validation
if (!filter_var($url, FILTER_VALIDATE_URL)) {
throw new \Exception('Invalid URL');
}
// Allowlist only known safe hosts
$allowedHosts = ['example.com', 'api.example.com'];
$host = parse_url($url, PHP_URL_HOST);
if (!in_array($host, $allowedHosts, true)) {
throw new \Exception('Host not allowed');
}
// Resolve host to IPs and reject private/internal ranges to mitigate SSRF to internal networks
$ips = @gethostbynamel($host);
if ($ips) {
foreach ($ips as $ip) {
if (is_private_ip($ip)) {
throw new \Exception('Internal network access blocked');
}
}
}
$resp = Http::timeout(5)->get($url);
if ($resp->successful()) {
echo $resp->body();
} else {
throw new \Exception('Remote fetch failed');
}
function is_private_ip($ip) {
if (strpos($ip, '10.') === 0) return true;
if (strpos($ip, '192.168.') === 0) return true;
if (strpos($ip, '127.') === 0) return true;
if (strpos($ip, '172.') === 0) {
$parts = explode('.', $ip);
$second = intval($parts[1]);
if ($second >= 16 && $second <= 31) return true;
}
return false;
}
?>