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Technical Overview
CVE-2026-84306 is a vulnerability in Filament, a collection of full-stack components for accelerated Laravel development. The flaw resides in the handling of one-time codes for app-based multi-factor authentication (MFA) within the `AppAuthentication.php` file located at packages/panels/src/Auth/MultiFactor/App/AppAuthentication.php.
The core issue lies in how the `AppAuthentication::verifyCode()` method implements its used-code cache mechanism. The cache key is derived from both the app authentication secret AND the submitted TOTP code. This design choice isolates the newest accepted timestep by the code itself rather than by the authentication secret.
Under normal circumstances, when a user submits a valid MFA code, the system should invalidate all previously issued codes for that authentication session. However, due to this cache key implementation, the system only prevents the exact same code from being reused. Any other code that falls within the accepted time window remains usable, even after a newer code has already been successfully used to authenticate.
The default configuration sets this time window to approximately four minutes. This means that if an attacker obtains both the user’s password and a single valid MFA code, that code remains valid for the remainder of its four-minute window. Even if the legitimate user logs in during that window using a different, newer code, the attacker’s captured code can still be used to gain unauthorized access.
Importantly, this vulnerability does not affect email-based MFA. The issue impacts Filament versions 4.0.0 through 4.12.5 and 5.0.0 through 5.7.5. The vulnerability has been patched in versions 4.12.6 and 5.7.6.
DailyCVE Form:
Platform: Filament (Laravel)
Version: 4.0.0-4.12.5, 5.0.0-5.7.5
Vulnerability: MFA code replay
Severity: Medium (CVSS 6.5)
Date: 2026-09-01
Prediction: Already patched (2026-09-01)
What Undercode Say:
Analytics & Detection
To determine if your Filament application is vulnerable, check the installed version:
composer show filament/filament
To identify potential exploitation attempts, monitor authentication logs for multiple MFA code submissions within a short time window:
grep "multi-factor" storage/logs/laravel.log | grep -E "code|verification" | awk '{print $1, $2, $NF}' | sort | uniq -c | sort -nr
Check for concurrent authentication sessions originating from different IP addresses:
grep "Authenticated" storage/logs/laravel.log | awk '{print $1, $2, $NF}' | sort | uniq -c | sort -nr
Exploit: (Educational Purposes!)
Attack Scenario:
- Attacker obtains target user’s password through phishing, credential stuffing, or other means.
- Attacker intercepts or phishes a single valid app-based MFA TOTP code from the target.
- Legitimate user enters a different, newer MFA code and successfully logs in.
- Attacker submits the intercepted code within the four-minute window.
- System accepts the older code because it is different from the already-used code.
6. Attacker gains unauthorized access to the account.
Conceptual Proof of Concept (for educational understanding only):
// Simplified illustration of the vulnerable logic
// packages/panels/src/Auth/MultiFactor/App/AppAuthentication.php
public function verifyCode($secret, $code, $window = 4)
{
$cacheKey = "mfa_used_{$secret}_{$code}"; // VULNERABLE: key includes both secret AND code
if (Cache::has($cacheKey)) {
return false; // Only blocks exact same code
}
$timesteps = $this->getTimesteps($code, $window);
foreach ($timesteps as $timestep) {
if ($this->verifyTimestep($secret, $timestep, $code)) {
Cache::put($cacheKey, true, 300); // Marks only this specific code as used
return true; // Different code within window remains valid
}
}
return false;
}
Protection:
- Immediate Action: Upgrade to Filament version 4.12.6 or 5.7.6 immediately:
composer require filament/filament:^4.12.6 OR composer require filament/filament:^5.7.6
- Code Review: If you cannot upgrade immediately, review `AppAuthentication::verifyCode()` and ensure the used-code cache key is derived solely from the authentication secret, not from the submitted code value.
- Configuration: Reduce the TOTP time window from the default four minutes to a shorter duration if your application requirements allow.
- Monitoring: Implement real-time monitoring for multiple MFA submissions from the same user account within a short time window.
Impact:
- Confidentiality (High): Attackers can gain unauthorized access to user accounts.
- Integrity (Low): Once authenticated, attackers may modify account settings or data.
- Availability (None): The vulnerability does not directly impact system availability.
- Attack Vector: Network-based exploitation.
- Attack Complexity: High – requires obtaining both password AND a valid MFA code.
- Privileges Required: None.
- User Interaction: None required for the attacker.
- Scope: Unchanged.
- CVSS v3.1 Score: 6.5 (Medium).
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Sources:
Reported By: github.com
Extra Source Hub:
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