Overview
Unrestricted Resource Consumption vulnerabilities in Laravel can arise when an authentication flow leaks information through timing differences, enabling attackers to perform iterative probing that consumes server resources while revealing valid credentials. The real-world CVE here is CVE-2017-14775, which describes how Laravel versions before 5.5.10 mishandled the remember_me token verification process because the DatabaseUserProvider does not perform a constant-time token comparison (CWE-200: Information Exposure). In practice, this means an attacker can observe small timing differences when tokens are correct versus incorrect, infer valid remember_me tokens, and potentially hijack remembered sessions without full login credentials. The root issue is the absence of a constant-time comparison during token verification, which opens a side-channel that can be abused under high-request loads or targeted token guessing attempts.
Affected Versions
< 5.5.10
Code Fix Example
Laravel API Security Remediation
Vulnerable:
<?php
$cookieToken = $_COOKIE['remember_token'] ?? '';
$dbToken = $user->remember_token;
if ($cookieToken == $dbToken) {
// authenticate the user via remember-me
}
?>
Fixed (constant-time comparison):
<?php
$cookieToken = $_COOKIE['remember_token'] ?? '';
$dbToken = $user->remember_token;
if (function_exists('hash_equals')) {
if (hash_equals($dbToken, $cookieToken)) {
// authenticate the user via remember-me
}
} else {
// Fallback for older PHP versions: implement a manual constant-time compare
$isEqual = (strlen($dbToken) === strlen($cookieToken));
if ($isEqual) {
$diff = 0;
for ($i = 0; $i < strlen($dbToken); $i++) {
$diff |= ord($dbToken[$i]) ^ ord($cookieToken[$i]);
}
$isEqual = ($diff === 0);
}
if ($isEqual) {
// authenticate the user via remember-me
}
}
?>