{"id":"GHSA-59f3-vp2f-mp9w","aliases":["CVE-2026-45755"],"title":"Symfony's Mailtrap Mailer Webhook Parser Never Verifies the X-Mt-Signature HMAC — Unauthenticated Webhook Event Injection","titleSource":"OSV","descriptionSource":"OSV","declaredSeverity":"MODERATE","description":"### 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the fix.","severity":"medium","score":6.6,"published":"2026-05-28T17:33:47.000Z","modified":"2026-09-10T03:50:45.630Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"Packagist","name":"symfony/mailtrap-mailer","sources":[{"name":"OSV · GHSA-59f3-vp2f-mp9w","url":"https://osv.dev/vulnerability/GHSA-59f3-vp2f-mp9w"}],"ranges":[{"events":[{"introduced":"7.2.0"},{"fixed":"7.4.12"}],"type":"ECOSYSTEM"}],"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"],"fixed":["7.4.12"]},{"ecosystem":"Packagist","name":"symfony/mailtrap-mailer","sources":[{"name":"OSV · GHSA-59f3-vp2f-mp9w","url":"https://osv.dev/vulnerability/GHSA-59f3-vp2f-mp9w"}],"ranges":[{"events":[{"introduced":"8.0.0"},{"fixed":"8.0.12"}],"type":"ECOSYSTEM"}],"versions":["v8.0.0"],"fixed":["8.0.12"]},{"ecosystem":"Packagist","name":"symfony/symfony","sources":[{"name":"OSV · GHSA-59f3-vp2f-mp9w","url":"https://osv.dev/vulnerability/GHSA-59f3-vp2f-mp9w"}],"ranges":[{"events":[{"introduced":"7.2.0"},{"fixed":"7.4.12"}],"type":"ECOSYSTEM"}],"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"],"fixed":["7.4.12"]},{"ecosystem":"Packagist","name":"symfony/symfony","sources":[{"name":"OSV · GHSA-59f3-vp2f-mp9w","url":"https://osv.dev/vulnerability/GHSA-59f3-vp2f-mp9w"}],"ranges":[{"events":[{"introduced":"8.0.0"},{"fixed":"8.0.12"}],"type":"ECOSYSTEM"}],"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"],"fixed":["8.0.12"]}],"sourceAffected":[],"references":["https://github.com/symfony/symfony/security/advisories/GHSA-59f3-vp2f-mp9w","https://github.com/symfony/symfony/commit/4e0467e4e182cf2e704a3d9e1bc1a6be65d52ab8","https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/mailtrap-mailer/CVE-2026-45755.yaml","https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45755.yaml","https://github.com/symfony/symfony","https://symfony.com/cve-2026-45755"],"sources":[{"name":"OSV","id":"GHSA-59f3-vp2f-mp9w","modified":"2026-09-10T03:50:45.630958598Z","url":"https://osv.dev/vulnerability/GHSA-59f3-vp2f-mp9w"}],"assessments":[{"source":"OSV","vector":"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","score":6.6}],"products":[],"remediation":[],"kev":{"status":"not-listed","checkedAt":"2026-10-28T21:55:33.923Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}