Summary
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.
Impact
A critical operation is accessible without requiring any authentication. Typical impact: any user can invoke the privileged function.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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symfony/symfony to 6.4.40 or later; symfony/symfony to 7.4.12 or later; symfony/symfony to 8.0.12 or later; symfony/twilio-notifier to 6.4.40 or later; symfony/twilio-notifier to 7.4.12 or later; symfony/twilio-notifier to 8.0.12 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-47212? CVE-2026-47212 is a medium-severity missing authentication for critical function vulnerability in symfony/symfony (composer), affecting versions >= 6.4.0, < 6.4.40. It is fixed in 6.4.40, 7.4.12, 8.0.12. A critical operation is accessible without requiring any authentication.
- Which packages are affected by CVE-2026-47212?
symfony/symfony(composer) (versions >= 6.4.0, < 6.4.40)symfony/twilio-notifier(composer) (versions >= 6.4.0, < 6.4.40)
- Is there a fix for CVE-2026-47212? Yes. CVE-2026-47212 is fixed in 6.4.40, 7.4.12, 8.0.12. Upgrade to this version or later.
- Is CVE-2026-47212 exploitable, and should I be worried? Whether CVE-2026-47212 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-47212 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-47212?
- Upgrade
symfony/symfonyto 6.4.40 or later - Upgrade
symfony/symfonyto 7.4.12 or later - Upgrade
symfony/symfonyto 8.0.12 or later - Upgrade
symfony/twilio-notifierto 6.4.40 or later - Upgrade
symfony/twilio-notifierto 7.4.12 or later - Upgrade
symfony/twilio-notifierto 8.0.12 or later
- Upgrade