Reflected XSS via unescaped slot name
Published Jun 22, 2026 · Updated Jun 22, 2026
Reflected XSS in Astro before 6.3.3 allows remote attackers to inject HTML through attacker-controlled slot names during SSR. The server renderer in packages/astro/src/runtime/server/render/component.ts interpolates the slot key directly into data-astro-template without HTML escaping, so crafted characters terminate the attribute and add markup. Exploitation requires an SSR route using a client:* directive to pass attacker-controlled data as a slot name and a user to load the reflected response, which executes script in the site's origin.
Summary
What happened
Reflected XSS in Astro before 6.3.3 allows remote attackers to inject HTML through attacker-controlled slot names during SSR. The server renderer in packages/astro/src/runtime/server/render/component.ts interpolates the slot key directly into data-astro-template without HTML escaping, so crafted characters terminate the attribute and add markup. Exploitation requires an SSR route using a client:* directive to pass attacker-controlled data as a slot name and a user to load the reflected response, which executes script in the site's origin.
The record
- CVE
- CVE-2026-50146
- Published
- Jun 22, 2026
- Updated
- Jun 22, 2026
- Vendor
- Astro Technology Company
- Product
- Astro
- Classifications
- CWE-80, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 22, 2026CVE publishedPublication date reported by the CVE source.
- Jun 22, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 6.3.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-8hv8-536x-4wqp proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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