CVE-2024-45047: Svelte Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-8266-84wp-wv5c
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2024-45047 is a MODERATE (CVSS 5.4) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Svelte libraries in the npm ecosystem. The issue involves svelte has a potential mxss vulnerability due to improper html escaping. Remediation is available by upgrading affected packages to version 4.2.19.

CVE-2024-45047 at a Glance

CVE Identifier CVE-2024-45047
GHSA Identifier GHSA-8266-84wp-wv5c
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Svelte
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.4

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:U/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 Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2024-45047

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

svelte fixed: 4.2.19 
npm install svelte@4.2.19
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 svelte

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2024-45047, inspect your project dependencies using npm:

npm ls svelte

Analyze the terminal output to locate any version of Svelte in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.2.19), your application is affected.

Note: The npm ls svelte 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 Svelte, 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

### Summary A potential XSS vulnerability exists in Svelte for versions prior to 4.2.19. ### Details Svelte improperly escapes HTML on server-side rendering. It converts strings according to the following rules: - If the string is an attribute value: - `"` -> `&quot;` - `&` -> `&amp;` - Other characters -> No conversion - Otherwise: - `<` -> `&lt;` - `&` -> `&amp;` - Other characters -> No conversion The assumption is that attributes will always stay as such, but in some situation the final DOM tree rendered on browsers is different from what Svelte expects on server-side rendering. This may be leveraged to perform XSS attacks. More specifically, this can occur when injecting malicious content into an attribute within a `<noscript>` tag. ### PoC A vulnerable page (`+page.svelte`): ```html <script> import { page } from "$app/stores" // user input let href = $page.url.searchParams.get("href") ?? "https://example.com"; </script> <noscript> <a href={href}>test</a> </noscript> ``` If a user accesses the following URL, ``` http://localhost:4173/?href=</noscript><script>alert(123)</script> ``` then, `alert(123)` will be executed. ### Impact XSS, when using an attribute within a noscript tag

CVE-2024-45047 Affected Svelte Versions

1 component(s)
Fixed Versions:
4.2.19
Product / Package Ecosystem Affected Versions Fixed Version
svelte
npm/svelte
npm
< 4.2.19
4.2.19

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sveltejs/svelte/security/advisories/GHSA-8266-84wp-wv5c
NVD — CVE-2024-45047 NVD
https://nvd.nist.gov/vuln/detail/CVE-2024-45047
Security Fix Commit FIX COMMIT
https://github.com/sveltejs/svelte/commit/83e96e044deb5ecbae2af361ae9e31d3e1ac43a3
Svelte Source Repository REPOSITORY
https://github.com/sveltejs/svelte

Frequently Asked Questions

What is CVE-2024-45047?
CVE-2024-45047 is a security vulnerability in Svelte involving Svelte has a potential mXSS vulnerability due to improper HTML escaping under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Svelte versions are affected?
Affected versions include releases prior to 4.2.19 across affected packages: svelte.
What version fixes CVE-2024-45047?
Upgrading to 4.2.19 (or the latest patched release for your respective branch) resolves the vulnerability.
Is svelte affected?
Yes, svelte is affected in releases prior to 4.2.19. Upgrade your dependency to 4.2.19 or later.
What is the CVSS score of CVE-2024-45047?
CVE-2024-45047 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2024-45047?
CVE-2024-45047 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-2024-45047?
Run the dependency tree command: 'npm ls svelte'. 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-8266-84wp-wv5c",
  "modified" : "2024-08-30T20:01:23Z",
  "published" : "2024-08-30T16:49:10Z",
  "aliases" : [ "CVE-2024-45047" ],
  "summary" : "Svelte has a potential mXSS vulnerability due to improper HTML escaping",
  "details" : "### Summary\n\nA potential XSS vulnerability exists in Svelte for versions prior to 4.2.19.\n\n### Details\n\nSvelte improperly escapes HTML on server-side rendering. It converts strings according to the following rules:\n\n- If the string is an attribute value:\n    - `\"` -> `&quot;`\n    - `&` -> `&amp;`\n    - Other characters -> No conversion\n- Otherwise:\n    - `<` -> `&lt;`\n    - `&` -> `&amp;`\n    - Other characters -> No conversion\n\nThe assumption is that attributes will always stay as such, but in some situation the final DOM tree rendered on browsers is different from what Svelte expects on server-side rendering. This may be leveraged to perform XSS attacks. More specifically, this can occur when injecting malicious content into an attribute within a `<noscript>` tag.\n\n### PoC\n\nA vulnerable page (`+page.svelte`):\n```html\n<script>\nimport { page } from \"$app/stores\"\n\n// user input\nlet href = $page.url.searchParams.get(\"href\") ?? \"https://example.com\";\n</script>\n\n<noscript>\n  <a href={href}>test</a>\n</noscript>\n```\n\nIf a user accesses the following URL,\n```\nhttp://localhost:4173/?href=</noscript><script>alert(123)</script>\n```\nthen, `alert(123)` will be executed.\n\n### Impact\n\nXSS, when using an attribute within a noscript tag",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "svelte"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.2.19"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/svelte/security/advisories/GHSA-8266-84wp-wv5c"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-45047"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/svelte/commit/83e96e044deb5ecbae2af361ae9e31d3e1ac43a3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sveltejs/svelte"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-08-30T16:49:10Z",
    "nvd_published_at" : "2024-08-30T17:15:15Z"
  }
}