vulnerability / NVI-00004176 / Revision 4
Symfony's Mailtrap Mailer Webhook Parser Never Verifies the X-Mt-Signature HMAC — Unauthenticated Webhook Event Injection
OSV carries this publisher advisory for symfony/mailtrap-mailer, symfony/mailtrap-mailer, symfony/symfony, symfony/symfony. This is an aggregated source copy; consult the original publisher and compare update dates.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
0.267%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.18867. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
symfony/mailtrap-mailer
source listedECOSYSTEM: introduced 7.2.0; fixed 7.4.12
### 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 i
symfony/mailtrap-mailer
source listedECOSYSTEM: introduced 8.0.0; fixed 8.0.12
### 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 i
symfony/symfony
source listedECOSYSTEM: introduced 7.2.0; fixed 7.4.12
### 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 i
symfony/symfony
source listedECOSYSTEM: introduced 8.0.0; fixed 8.0.12
### 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 i
03 / Response
What to do next
- vendor patch
The original advisory lists fixed boundaries 7.4.12 for symfony/mailtrap-mailer. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- vendor patch
The original advisory lists fixed boundaries 8.0.12 for symfony/mailtrap-mailer. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- vendor patch
The original advisory lists fixed boundaries 7.4.12 for symfony/symfony. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- vendor patch
The original advisory lists fixed boundaries 8.0.12 for symfony/symfony. Confirm the publisher’s latest guidance.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database via OSV
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-59f3-vp2f-mp9w ↗
GitHub Advisory Database via OSV · vendor advisory
Observed . GitHub-origin advisory, CC-BY-4.0; OSV is an aggregate copy, not independent corroboration.
- CVE-2026-45755 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 4 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 3 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.