{"id":"CVE-2026-45755","aliases":["GHSA-59f3-vp2f-mp9w"],"url":"https://o3.security/vulnerability/CVE-2026-45755","summary":"Symfony: Mailtrap Mailer Webhook Parser Never Verifies the X-Mt-Signature HMAC — Unauthenticated Webhook Event Injection","details":"### Description\n\nThe Mailtrap mailer bridge ships a webhook request parser used to authenticate and decode the event callbacks Mailtrap POSTs to an application's webhook endpoint. Its `doParse(Request $request, #[\\SensitiveParameter] string $secret)` method receives the configured webhook secret but never reads it; it decodes and returns the payload unconditionally, ignoring the `X-Mt-Signature` HMAC header Mailtrap sends with each request.\n\nAs a result, an application that wires up the Mailtrap webhook endpoint accepts **any** POST to that URL, even when a signing secret is configured (the recommended setup). An attacker who knows the endpoint exists can submit forged event payloads, fake delivery / bounce / open / click / spam events, leading to suppression-list corruption, delivery-metrics fraud, etc.\n\n### Resolution\n\n`MailtrapRequestParser::doParse()` now requires and verifies the `X-Mt-Signature` header, an HMAC-SHA256 of the raw request body keyed with the configured secret, before decoding the payload, using a constant-time comparison.\n\nWhen no secret is configured the behaviour is unchanged: signature verification remains opt-in, but it is now actually enforced once opted in.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/4e0467e4e182cf2e704a3d9e1bc1a6be65d52ab8) for branch 7.4.\n\n### Credits\n\nSymfony would like to thank Himanshu Anand for reporting the issue and Alexandre Daubois providing the fix.","published":"2026-07-14T18:56:20.615Z","modified":"2026-08-12T03:51:25.471140577Z","cvss":null,"epss":{"score":0.00267,"percentile":0.18503,"asOf":"2026-08-31"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"symfony/mailtrap-mailer","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/mailtrap-mailer","fixedVersion":"8.0.12"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"8.0.12"}],"fix":{"url":"https://github.com/symfony/symfony/commit/4e0467e4e182cf2e704a3d9e1bc1a6be65d52ab8","label":"symfony/symfony@4e0467e"},"references":[{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v7.4.12"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v8.0.12"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45755.json"},{"type":"ADVISORY","url":"https://github.com/symfony/symfony/security/advisories/GHSA-59f3-vp2f-mp9w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45755"},{"type":"FIX","url":"https://github.com/symfony/symfony/commit/4e0467e4e182cf2e704a3d9e1bc1a6be65d52ab8"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/mailtrap-mailer/CVE-2026-45755.yaml"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45755.yaml"},{"type":"PACKAGE","url":"https://github.com/symfony/symfony"},{"type":"WEB","url":"https://symfony.com/cve-2026-45755"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:25.471140577Z"}}