GHSA-59f3-vp2f-mp9w
Fix: symfony/symfony@4e0467eGHSA-59f3-vp2f-mp9w is a Missing Authentication vulnerability in symfony/mailtrap-mailer. O3 Security confirms whether GHSA-59f3-vp2f-mp9w is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Symfony's Mailtrap Mailer Webhook Parser Never Verifies the X-Mt-Signature HMAC — Unauthenticated Webhook Event Injection
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-59f3-vp2f-mp9w.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
symfony/mailtrap-mailer🐘symfony/mailtrap-mailer🐘symfony/symfony🐘symfony/symfonyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Description
The 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.
As 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.
Resolution
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.
When no secret is configured the behaviour is unchanged: signature verification remains opt-in, but it is now actually enforced once opted in.
The patch for this issue is available here for branch 7.4.
Credits
Symfony would like to thank Himanshu Anand for reporting the issue and Alexandre Daubois providing the fix.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | symfony/mailtrap-mailer | ≥ 7.2.0&&< 7.4.12 | 7.4.12 |
| 🐘Packagist | symfony/mailtrap-mailer | ≥ 8.0.0&&< 8.0.12 | 8.0.12 |
| 🐘Packagist | symfony/symfony | ≥ 7.2.0&&< 7.4.12 | 7.4.12 |
| 🐘Packagist | symfony/symfony | ≥ 8.0.0&&< 8.0.12 | 8.0.12 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/mailtrap-mailer. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update symfony/mailtrap-mailer to 7.4.12 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-59f3-vp2f-mp9w is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-59f3-vp2f-mp9w is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-59f3-vp2f-mp9w. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-59f3-vp2f-mp9w in your dependencies?
O3 detects GHSA-59f3-vp2f-mp9w across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.