Bypass of CSRF Middleware in Astro

Vulnerability Description

Astro is a web framework for content-driven websites. In affected versions a bug in Astro’s CSRF-protection middleware allows requests to bypass CSRF checks. When the `security.checkOrigin` configuration option is set to `true`, Astro middleware will perform a CSRF check. However, a vulnerability exists that can bypass this security. A semicolon-delimited parameter is allowed after the type in `Content-Type`. Web browsers will treat a `Content-Type` such as `application/x-www-form-urlencoded; abc` as a `simple request` and will not perform preflight validation. In this case, CSRF is not blocked as expected. Additionally, the `Content-Type` header is not required for a request. This issue has been addressed in version 4.16.17 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

References

• https://github.com/withastro/astro/security/advisories/GHSA-c4pw-33h3-35xw
• https://github.com/withastro/astro/commit/e7d14c374b9d45e27089994a4eb72186d05514de
• https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#simple_requests
• https://github.com/withastro/astro/blob/6031962ab5f56457de986eb82bd24807e926ba1b/packages/astro/src/core/app/middlewares.ts