{"id":"GHSA-59f3-vp2f-mp9w","summary":"Symfony's 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.","aliases":["CVE-2026-45755"],"modified":"2026-09-10T03:50:45.630958598Z","published":"2026-05-28T17:33:47Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-05-28T17:33:47Z","nvd_published_at":null,"cwe_ids":["CWE-306","CWE-347"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/symfony/symfony/security/advisories/GHSA-59f3-vp2f-mp9w"},{"type":"WEB","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"}],"affected":[{"package":{"name":"symfony/mailtrap-mailer","ecosystem":"Packagist","purl":"pkg:composer/symfony/mailtrap-mailer"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.12"}]}],"versions":["v7.2.0","v7.3.0","v7.3.0-BETA1","v7.3.0-RC1","v7.4.0","v7.4.0-BETA1","v7.4.0-RC1"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-59f3-vp2f-mp9w/GHSA-59f3-vp2f-mp9w.json"}},{"package":{"name":"symfony/mailtrap-mailer","ecosystem":"Packagist","purl":"pkg:composer/symfony/mailtrap-mailer"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.12"}]}],"versions":["v8.0.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-59f3-vp2f-mp9w/GHSA-59f3-vp2f-mp9w.json"}},{"package":{"name":"symfony/symfony","ecosystem":"Packagist","purl":"pkg:composer/symfony/symfony"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.4.12"}]}],"versions":["v7.2.0","v7.2.1","v7.2.2","v7.2.3","v7.2.4","v7.2.5","v7.2.6","v7.2.7","v7.2.8","v7.2.9","v7.3.0","v7.3.0-BETA1","v7.3.0-BETA2","v7.3.0-RC1","v7.3.1","v7.3.10","v7.3.11","v7.3.2","v7.3.3","v7.3.4","v7.3.5","v7.3.6","v7.3.7","v7.3.8","v7.3.9","v7.4.0","v7.4.0-BETA1","v7.4.0-BETA2","v7.4.0-RC1","v7.4.0-RC2","v7.4.0-RC3","v7.4.1","v7.4.10","v7.4.11","v7.4.2","v7.4.3","v7.4.4","v7.4.5","v7.4.6","v7.4.7","v7.4.8","v7.4.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-59f3-vp2f-mp9w/GHSA-59f3-vp2f-mp9w.json"}},{"package":{"name":"symfony/symfony","ecosystem":"Packagist","purl":"pkg:composer/symfony/symfony"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.12"}]}],"versions":["v8.0.0","v8.0.1","v8.0.10","v8.0.11","v8.0.2","v8.0.3","v8.0.4","v8.0.5","v8.0.6","v8.0.7","v8.0.8","v8.0.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-59f3-vp2f-mp9w/GHSA-59f3-vp2f-mp9w.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U"}]}