CVE-2026-45028 Astro: Server island encrypted parameters vulnerable to cross-component replay
Attackers can replay encrypted parameters to inject malicious HTML, leading to XSS in Astro applications using server islands.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45028?
CVE-2026-45028 is a low-severity cross-site scripting vulnerability in withastro astro, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Astro is a web framework. Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (p) value as another component's slots (s) value, or vice versa. Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications. This occurs when the application uses server islands, two different server island components share the same key name for a prop and a slot, and an attacker has full control over the value of the overlapping prop (requires a dynamically rendered page). This vulnerability is fixed in 6.1.10.
Which versions are affected by CVE-2026-45028?
2 open source packages ship an affected version, including astro. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
astro npm | All versions | 6.1.10 |
astro npm | All versions | 6.1.10 |
Products include Astro Astro.
How do I fix CVE-2026-45028?
Upgrade astro to 6.1.10 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-2026-45028 being exploited?
There is no known exploitation of CVE-2026-45028 in the wild and no public exploit code.
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-2026-1789031241, CLSA-2026-1792161562, CLSA-2026-1792161707, CLSA-2026-1792161794, CLSA-2026-1792161859, GHSA-xr5h-phrj-8vxv.