Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M

CVE-2026-50146Astro: Reflected XSS via unescaped slot name

High 7.1

In plain English

A high-severity security flaw in astro from withastro. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.1High

Exploit odds (30 days)0.3%top 80.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Astro is a web framework. Prior to 6.3.3, when a component uses a client:* directive, Astro inserts named slot content into a data-astro-template attribute without HTML escaping the slot name allowing an attacker to break out of the attribute context and inject arbitrary HTML, resulting in reflected XSS during SSR. This vulnerability is fixed in 6.3.3.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	astro	6.3.3	GHSA-8hv8-536x-4wqp

Affected products (as reported)

Vendor	Product	Versions
withastro	astro	< 6.3.3

Weakness: CWE-80 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N

References

https://github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp x_refsource_CONFIRM