# 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.

- **Severity:** Low 2.9 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 May 2026
- **Updated:** 14 May 2026
- **Also known as:** CLSA-2026-1789031241, CLSA-2026-1792161562, CLSA-2026-1792161707, CLSA-2026-1792161794, CLSA-2026-1792161859, GHSA-xr5h-phrj-8vxv

## 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-323 (Reusing a Nonce, Key Pair in Encryption)

## Which versions are affected by CVE-2026-45028?

2 open source packages ship an affected version, including astro. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `astro` | npm | All versions | 6.1.10 |
| `astro` | npm | All versions | 6.1.10 |

Products: Astro Astro.

## How do I fix CVE-2026-45028?

Upgrade astro to 6.1.10 or later.

## 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](https://insights.sbomify.com/CVE-2024-56159/): Server source code is exposed to the public if sourcemaps are enabled (high 7.8)
- [CVE-2026-54299](https://insights.sbomify.com/CVE-2026-54299/): Astro: Host header SSRF in prerendered error page fetch (high 7.5)
- [CVE-2025-59837](https://insights.sbomify.com/CVE-2025-59837/): astro allows bypass of image proxy domain validation leading to SSRF and potential XSS (high 7.2)
- [CVE-2026-50146](https://insights.sbomify.com/CVE-2026-50146/): Astro: Reflected XSS via unescaped slot name (high 7.1)
- [CVE-2025-64764](https://insights.sbomify.com/CVE-2025-64764/): Astro is vulnerable to Reflected XSS via the server islands feature (high 7.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45028 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-45028 in the wild and no public exploit code.

Affected packages and fixed versions:
- astro (npm): affected all versions; fixed in 6.1.10
- astro (npm): affected all versions; fixed in 6.1.10

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-45028/ (Markdown: https://insights.sbomify.com/CVE-2026-45028/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45028
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45028
- OSV: https://osv.dev/vulnerability/CVE-2026-45028

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45028/
Summaries are generated and may contain mistakes; the official description above is the record.