Medium severity · published Jun 22, 2026
CVE-2026-50146
Astro: Reflected XSS via unescaped slot name
6.1
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 19% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AS
astro · withastro
< 6.3.3 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50146
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-50146
Exploit
https://github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp
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