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The Mailjet mailer bridge and the LOX24 SMS notifier bridge both ship webhook request parsers used to authenticate and decode the event callbacks each provider POSTs to an application’s webhook endpoint. Their `doParse(Request $request, [\SensitiveParameter] string $secret)` methods receive the configured webhook secret but never read it; they convert and return the payload unconditionally.
As a result, an application that wires up either webhook endpoint accepts any POST to that URL, even when a webhook secret is configured (the recommended setup). The `doParse` method ignores the `$secret` parameter entirely—it does not compare the secret against anything in the request. This means an attacker who knows the endpoint exists can submit forged event payloads, fake bounce / blocked / spam / open / click / delivery events, leading to suppression-list corruption, delivery-metrics fraud, and similar abuse.
The vulnerability affects both bridges. For Mailjet, the parser never checks for any authentication token. For LOX24, the parser similarly discards the secret. In both cases, the secret is passed into the method but is never used to validate the incoming webhook. This breaks the security model of webhooks, which rely on shared secrets to ensure that only the legitimate provider can trigger events.
The fix introduces proper authentication checks. The Mailjet parser now rejects requests unless they carry HTTP Basic credentials that match the configured secret, using a constant-time comparison. The LOX24 parser now rejects requests unless they include an `X-LOX24-Token` header with a value that matches the secret, also using a constant-time comparison. When no secret is configured, the behavior remains unchanged, keeping authentication opt‑in.
DailyCVE Form:
Platform: Symfony Webhook Bridges
Version: Symfony 6.4.0-8.0.11
Vulnerability : Missing Authentication Validation
Severity: Moderate
date: 2026‑05‑20
Prediction: Already Patched
Analytics under heading What Undercode Say:
Check Symfony version
composer show symfony/symfony | grep versions
Test Mailjet webhook vulnerability
curl -X POST https://your-app.com/webhook/mailjet \
-H "Content-Type: application/json" \
-d '{"event":"bounce","email":"[email protected]"}'
Test LOX24 webhook vulnerability
curl -X POST https://your-app.com/webhook/lox24 \
-H "Content-Type: application/json" \
-d '{"status":"delivered","id":"123"}'
Apply Mailjet patch (6.4 branch)
composer require symfony/mailjet-mailer:^6.4.40
Apply LOX24 patch (7.4 branch)
composer require symfony/lox24-notifier:^7.4.12
Exploit:
An attacker can send crafted POST requests to the exposed webhook endpoints without any authentication. For Mailjet, the request must include HTTP Basic credentials (any username, any password will be accepted). For LOX24, the request must include an `X-LOX24-Token` header (any value will be accepted). The parser will process the payload as if it came from the legitimate provider, allowing the attacker to inject fake events such as bounce, blocked, spam, open, click, or delivery notifications. This can corrupt suppression lists, skew delivery metrics, and potentially mark legitimate emails as bounced.
Protection:
Upgrade to patched versions immediately. For Mailjet, upgrade to 6.4.40, 7.4.12, or 8.0.12 or later. For LOX24, upgrade to 7.4.12, 8.0.12 or later. If upgrading is not possible, implement a custom middleware that validates the webhook secret manually before passing the request to the parser. Ensure the webhook endpoint is not publicly exposed or is protected by an API gateway that enforces authentication. Monitor webhook logs for unexpected events.
Impact:
Unauthenticated attackers can inject arbitrary webhook events, leading to:
– Suppression-list corruption: Fake bounce events can add valid email addresses to suppression lists, preventing legitimate emails from being delivered.
– Delivery-metrics fraud: Fake open, click, or delivery events can inflate metrics, making campaigns appear more successful than they are.
– Reputation damage: False spam reports can harm sender reputation.
– Operational disruption: Fake block events can cause legitimate emails to be dropped.
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Sources:
Reported By: github.com
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