Use of Non-Canonical URL Paths for Authorization Decisions Affecting astro package, versions <5.16.3
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-ASTRO-14235580
- published12 Dec 2025
- disclosed8 Dec 2025
- creditzomaxsec
Introduced: 8 Dec 2025
NewCVE-2025-66202 (opens in a new tab)How to fix?
Upgrade astro to version 5.16.3 or higher.
Overview
astro is an Astro is a modern site builder with web best practices, performance, and DX front-of-mind.
Affected versions of this package are vulnerable to Use of Non-Canonical URL Paths for Authorization Decisions due to improper URL decoding logic. The pathname validation used for protecting routes decodes the request path only once, allowing double-encoded sequences to bypass path-based authentication checks. An attacker can exploit this by submitting double-encoded URLs to access protected routes such as /admin or /api/internal, enabling unauthorized access to restricted functionality.
Note: There has been an attempt to fix this vulnerability in version 5.15.8 following CVE-2025-64765, but the fix is insufficient.