Symfony: Twilio SMS Notifier allows unauthenticated webhook injection due to missing X-Twilio-Signature verification
Description
The Twilio SMS notifier bridge ships a webhook request parser used to authenticate and decode the status callbacks Twilio 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-Twilio-Signature HMAC header Twilio sends with each request.
As a result, an application that wires up the Twilio 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 status payloads, fake delivered / failed / undelivered events, leading to delivery-metrics fraud, downstream automation triggers, etc.
Resolution
TwilioRequestParser::doParse() now requires and verifies the X-Twilio-Signature header (HMAC-SHA1 over the full request URL concatenated with the alphabetically-sorted POST parameters, base64-encoded, keyed with the Twilio account auth token) before further processing, 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.
Applications behind a TLS-terminating reverse proxy must configure framework.trusted_proxies and framework.trusted_headers so that Request::getUri() returns the public URL Twilio signed.
The patch for this issue is available here for branch 6.4.
Credits
Symfony would like to thank Himanshu Anand for reporting the issue and Nicolas Grekas for providing the fix.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | symfony/symfony | >= 6.4.0, < 6.4.40, >= 7.0.0, < 7.4.12, >= 8.0.0, < 8.0.12 | 6.4.40, 7.4.12, 8.0.12 |
| Composer package | symfony/twilio-notifier | >= 6.4.0, < 6.4.40, >= 7.0.0, < 7.4.12, >= 8.0.0, < 8.0.12 | 6.4.40, 7.4.12, 8.0.12 |
References
- https://github.com/symfony/symfony/security/advisories/GHSA-55rj-x2vc-4whq
- https://github.com/symfony/symfony/commit/8545fb2af6c07dfb5ef0fc8d9bccf86db2c94356
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-47212.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/twilio-notifier/CVE-2026-47212.yaml
- https://github.com/symfony/symfony
- https://symfony.com/cve-2026-47212
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-306, CWE-347- Platform
- Composer
- Package
symfony/symfony, symfony/twilio-notifier- Disclosed
- 29.05.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-55rj-x2vc-4whq - CC BY 4.0
Vulnerability history: symfony/twilio-notifier
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.