What is CVE-2026-50146?

CVE-2026-50146 is a high-severity vulnerability in Astro, classified under Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS). CVSS score: 7.1/10. Published 2026-06-22.

How severe is CVE-2026-50146?

High severity. CVSS v3 base score is 7.1 out of 10.

XSS in Astro

CVE-2026-50146

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.

Published 2026-06-22 · last modified 2026-06-23.

CVSS v3 metric

CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N.

EPSS exploit prediction

EPSS: 0.003 (17.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 17.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Astro
Withastro Astro — versions < 6.3.3

Weakness classification (CWE)

CWE-80 — Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

References

github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp (Exploit, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-50146?: CVE-2026-50146 is a high-severity vulnerability in Astro, classified under Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS). CVSS score: 7.1/10. Published 2026-06-22.
How severe is CVE-2026-50146?: High severity. CVSS v3 base score is 7.1 out of 10.