CVE-2026-54298: Astro: XSS via Unescaped Attribute Names in Spread Props

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-22 · updated 2026-10-25
Weakness: CWE-79

Description

Astro is a web framework. Prior to 6.4.6, the spreadAttributes function in Astro's server-side rendering pipeline iterates over object keys and passes them directly to addAttribute, which interpolates the key into the HTML output without escaping. When a developer uses the spread syntax {...props} on an HTML element and the object keys come from an untrusted source (API, CMS, URL parameters), an attacker can inject arbitrary HTML attributes including event handlers like onmousemove, onclick, or break out of the attribute context entirely to inject new elements. This vulnerability is fixed in 6.4.6.

Affected products

withastro astro: before 6.4.6 — fixed in 6.4.6

How to fix

Upgrade to a fixed version: withastro astro 6.4.6. Check the vendor advisory for mitigations.

References

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