What’s Vulnerable › Vulnerabilities

CVE-2026-41067: Astro: XSS via incomplete `</script>` sanitization in `define:vars` allows case-insensitive and whitespace-based bypass

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-24 · updated 2026-10-26
• Weakness: CWE-79

Description

Astro is a web framework. Prior to 6.1.6, the defineScriptVars function in Astro's server-side rendering pipeline uses a case-sensitive regex /<\/script>/g to sanitize values injected into inline <script> tags via the define:vars directive. HTML parsers close <script> elements case-insensitively and also accept whitespace or / before the closing >, allowing an attacker to bypass the sanitization with payloads like </Script>, </script >, or </script/> and inject arbitrary HTML/JavaScript. This vulnerability is fixed in 6.1.6.

Affected products

• withastro astro: before 6.1.6 — fixed in 6.1.6

How to fix

Upgrade to a fixed version: withastro astro 6.1.6. Check the vendor advisory for mitigations.

References

• https://github.com/withastro/astro/security/advisories/GHSA-j687-52p2-xcff
• https://github.com/withastro/astro/security/advisories/GHSA-j687-52p2-xcff

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