CVE-2025-66202
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 24% of all known CVEs.
References
Related Vulnerabilities
Other CWE-647 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-43939 | High | 8.6 | 92% | KEV | Fix |
| CVE-2025-64500 | High | 7.3 | 1.3% | - | Fix |
| CVE-2026-5222 | Low | 6.5 | 0.5% | - | Fix |
| CVE-2025-47241 | Medium | 4.0 | 0.5% | - | - |
| CVE-2026-62685 | High | 8.1 | 0.3% | - | - |
| CVE-2026-59731 | High | 8.2 | 0.3% | - | - |
Common questions
How do I fix CVE-2025-66202?
Upgrade astro to 5.15.8 or later.
Is CVE-2025-66202 being actively exploited?
Not that we know of. CVE-2025-66202 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.32% is the estimated probability that it will be exploited in the next 30 days. That is higher than 24% of all scored CVEs.
How severe is CVE-2025-66202?
CVE-2025-66202 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2025-66202 affect?
Published advisories record a fix for astro (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-12-10.