CVE-2025-66202: astro — Fix

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.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Weakness Type (CWE)

CWE-647 CWE-647

Affected Products

Vendor	Product	Versions
astro	astro	< 5.15.8

References

Advisories & Patches

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

Other References

https://github.com/withastro/astro/security/advisories/GHSA-ggxq-hp9w-j794

Frequently Asked Questions

What is CVE-2025-66202? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2025-66202? +

CVE-2025-66202 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-66202? +

CVE-2025-66202 affects products from astro, specifically: astro. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-66202? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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