Symfony's Mailtrap Mailer Webhook Parser Never Verifies the X-Mt-Signature HMAC — Unauthenticated Webhook Event Injection

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0027, the 19th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 20 May 2026, 10:21 UTC Published by the maintainers as a GitHub repository advisory
2. 31 Oct 2026, 14:02 UTC First seen by agentprime
3. 31 Oct 2026, 14:02 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-59f3-vp2f-mp9w
• OSV: GHSA-59f3-vp2f-mp9w
• github.com/symfony/symfony/security/advisories/GHSA-59f3-vp2f-mp9w
• github.com/symfony/symfony/commit/4e0467e4e182cf2e704a3d9e1bc1a6be65d52ab8
• github.com/FriendsOfPHP/security-advisories/blob/master/symfony/mailtrap-mailer/CVE-2026-45755.yaml
• github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45755.yaml
• github.com/symfony/symfony
• symfony.com/cve-2026-45755

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.