Overview
CVE-2017-14775 describes a flaw in Laravel before 5.5.10 where the remember_me token verification in the DatabaseUserProvider did not perform a constant-time comparison, enabling a timing side-channel and potential information disclosure (CWE-200). This is a form of improper inventory management of authentication state tokens, where sensitive tokens are compared without constant-time guarantees, increasing the risk of token inference or misuse. In real-world deployments, persistent login tokens (remember_me cookies) can be probed or observed by an attacker, potentially leading to unauthorized sessions if tokens are guessed or manipulated over time.
In practice, an attacker who can observe or control a remember_me cookie could perform token probing and timing measurements to determine whether a candidate token matches the one stored for a given user. Because the comparison was not constant-time, small timing differences could reveal partial information about the token, enabling incremental guessing attacks. This falls under CWE-200 (Information Exposure) and highlights how improper handling and verification of tokens constitutes an inventory-management flaw in how authentication state is stored and verified.
Remediation for this class of vulnerability centers on ensuring constant-time token comparisons and robust token handling. Upgrading Laravel to a version that includes the fix (5.5.10 or later) mitigates the issue, and developers should audit authentication flows to replace insecure equality checks with constant-time comparisons (for example, hash_equals). Additionally, rotate remember_me tokens, validate token handling in custom providers, and add tests to verify timing-safe comparisons to prevent regressions.
Affected Versions
<5.5.10
Code Fix Example
Laravel API Security Remediation
<?php
// Vulnerable pattern (non-constant-time comparison)
$rememberToken = $_COOKIE['remember_token'] ?? null;
$user = App\\Models\\User::where('email', $email)->first();
if ($user && $user->remember_token == $rememberToken) {
Auth::login($user);
}
// Fixed pattern (constant-time comparison)
$rememberToken = $_COOKIE['remember_token'] ?? null;
$user = App\\Models\\User::where('email', $email)->first();
if ($user && hash_equals((string) ($user->remember_token ?? ''), (string) $rememberToken)) {
Auth::login($user);
}
?>