Astro: Reflected XSS via unescaped slot name

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Summary

CVECVE-2026-50146
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-22 19:17:04 UTC
Updated2026-06-23 15:16:35 UTC
DescriptionAstro 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.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS: 0.001770000 probability, percentile 0.074870000 (date 2026-06-27)

Problem Types: CWE-80 | CWE-80 CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary6.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
3.1[email protected]Secondary7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N
3.1CNADECLARED7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Astro Astro All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Withastro Astro affected < 6.3.3 Not specified

References

ReferenceSourceLinkTags
github.com/withastro/astro/security/advisories/GHSA-8hv8-536x-4wqp 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com Exploit, Mitigation, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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