CVE-2026-45028: Astro Server Island Encrypted Parameters Vulnerable Vulnerability

LOW
Advisory Identifier: GHSA-xr5h-phrj-8vxv
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CVSS 6.1
CWE-79 CWE-323
Published
Advisory Summary

CVE-2026-45028 is a LOW (CVSS 6.1) server island encrypted parameters vulnerable vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Astro libraries in the npm ecosystem. The issue involves server island encrypted parameters vulnerable to cross-component replay. Remediation is available by upgrading affected packages to version 6.1.10.

CVE-2026-45028 at a Glance

CVE Identifier CVE-2026-45028
GHSA Identifier GHSA-xr5h-phrj-8vxv
Severity LOW
CVSS v3.1 Base Score 6.1
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Astro
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-45028

To remediate this vulnerability, upgrade all affected Astro dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

astro fixed: 6.1.10 
npm install astro@6.1.10
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls astro

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-45028, inspect your project dependencies using npm:

npm ls astro

Analyze the terminal output to locate any version of Astro in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.1.10), your application is affected.

Note: The npm ls astro command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Astro, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact 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 that meet **all** of the following conditions: - The application uses server islands - Two different server island components share the same key name for a prop and a slot - An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page) These conditions are very unlikely to occur in real-world production applications. ### Patches This has been patched in **astro@6.1.10**. The fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like `props:IslandName` or `slots:IslandName`, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots. ### References - Fix PR: https://github.com/withastro/astro/pull/16457 - Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical

CVE-2026-45028 Affected Astro Versions

1 component(s)
Fixed Versions:
6.1.10
Product / Package Ecosystem Affected Versions Fixed Version
astro
npm/astro
npm
< 6.1.10
6.1.10

References

GitHub Advisory / Wiki ADVISORY
https://github.com/withastro/astro/security/advisories/GHSA-xr5h-phrj-8vxv
NVD — CVE-2026-45028 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-45028
Astro Source Repository REPOSITORY
https://github.com/withastro/astro/pull/16457
Security Fix Commit FIX COMMIT
https://github.com/withastro/astro/commit/3d82220a1549e699e34ed433f3846a919f4c02bd
Astro Source Repository REPOSITORY
https://github.com/withastro/astro

Frequently Asked Questions

What is CVE-2026-45028?
CVE-2026-45028 is a security vulnerability in Astro involving Server island encrypted parameters vulnerable to cross-component replay under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Astro versions are affected?
Affected versions include releases prior to 6.1.10 across affected packages: astro.
What version fixes CVE-2026-45028?
Upgrading to 6.1.10 (or the latest patched release for your respective branch) resolves the vulnerability.
Is astro affected?
Yes, astro is affected in releases prior to 6.1.10. Upgrade your dependency to 6.1.10 or later.
What is the CVSS score of CVE-2026-45028?
CVE-2026-45028 has a CVSS v3.1 base score of 6.1 (LOW) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-45028?
CVE-2026-45028 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check npm dependencies for CVE-2026-45028?
Run the dependency tree command: 'npm ls astro'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xr5h-phrj-8vxv",
  "modified" : "2026-05-14T20:38:54Z",
  "published" : "2026-05-13T01:36:39Z",
  "aliases" : [ "CVE-2026-45028" ],
  "summary" : "Astro: Server island encrypted parameters vulnerable to cross-component replay",
  "details" : "### Impact\n\nAstro 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.\n\nSince slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications that meet **all** of the following conditions:\n\n- The application uses server islands\n- Two different server island components share the same key name for a prop and a slot\n- An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page)\n\nThese conditions are very unlikely to occur in real-world production applications.\n\n### Patches\n\nThis has been patched in **astro@6.1.10**.\n\nThe fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like `props:IslandName` or `slots:IslandName`, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots.\n\n### References\n\n- Fix PR: https://github.com/withastro/astro/pull/16457\n- Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "astro"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.1.10"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/security/advisories/GHSA-xr5h-phrj-8vxv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-45028"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/pull/16457"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/withastro/astro/commit/3d82220a1549e699e34ed433f3846a919f4c02bd"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/withastro/astro"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-323", "CWE-79" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-13T01:36:39Z",
    "nvd_published_at" : "2026-05-13T16:17:00Z"
  }
}