Astro middleware authentication checks based on url.pathname can be bypassed via url encoded values

Vulnerability Description

Astro is a web framework. Prior to version 5.15.8, a mismatch exists between how Astro normalizes request paths for routing/rendering and how the application’s middleware reads the path for validation checks. Astro internally applies decodeURI() to determine which route to render, while the middleware uses context.url.pathname without applying the same normalization (decodeURI). This discrepancy may allow attackers to reach protected routes using encoded path variants that pass routing but bypass validation checks. This issue has been patched in version 5.15.8.

References

• https://github.com/withastro/astro/security/advisories/GHSA-ggxq-hp9w-j794
• https://github.com/withastro/astro/commit/6f800813516b07bbe12c666a92937525fddb58ce