CVE-2026-54298 Astro: XSS via Unescaped Attribute Names in Spread Props
Attackers can inject malicious scripts via unescaped attribute names in spread props, requiring developers to upgrade Astro.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-54298?
CVE-2026-54298 is a medium-severity cross-site scripting vulnerability in withastro astro, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-54298?
2 open source packages ship an affected version, including astro. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
astro npm | All versions | 6.4.6 |
astro npm | All versions | 6.4.6 |
Products include Astro Astro.
How do I fix CVE-2026-54298?
Upgrade astro to 6.4.6 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-54298 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54298 exists.
Other vulnerabilities in withastro astro
- CVE-2024-56159 Server source code is exposed to the public if sourcemaps are enabled
- CVE-2026-54299 Astro: Host header SSRF in prerendered error page fetch
- CVE-2025-59837 astro allows bypass of image proxy domain validation leading to SSRF and potential XSS
- CVE-2026-50146 Astro: Reflected XSS via unescaped slot name
- CVE-2025-64764 Astro is vulnerable to Reflected XSS via the server islands feature
Sources
Also known as CLSA-2026-1784596276, CLSA-2026-1784596300, CLSA-2026-1792161691, CLSA-2026-1792161695, GHSA-jrpj-wcv7-9fh9.