CVE-2021-39178: Next Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-9gr3-7897-pp7m
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CVSS 7.5
CWE-79
Published
Advisory Summary

CVE-2021-39178 is a HIGH (CVSS 7.5) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Next libraries in the npm ecosystem. The issue involves xss in image optimization api for next.js. Remediation is available by upgrading affected packages to version 11.1.1.

CVE-2021-39178 at a Glance

CVE Identifier CVE-2021-39178
GHSA Identifier GHSA-9gr3-7897-pp7m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Next
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

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

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-39178

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

next fixed: 11.1.1 
npm install next@11.1.1
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 next

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-39178, inspect your project dependencies using npm:

npm ls next

Analyze the terminal output to locate any version of Next in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 11.1.1), your application is affected.

Note: The npm ls next 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 Next, 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 - **Affected:** All of the following must be true to be affected - Next.js between version 10.0.0 and 11.1.0 - The `next.config.js` file has [`images.domains`](https://nextjs.org/docs/basic-features/image-optimization#domains) array assigned - The image host assigned in [`images.domains`](https://nextjs.org/docs/basic-features/image-optimization#domains) allows user-provided SVG - **Not affected**: The `next.config.js` file has [`images.loader`](https://nextjs.org/docs/basic-features/image-optimization#loader) assigned to something other than default - **Not affected**: Deployments on [Vercel](https://vercel.com) are not affected ### Patches [Next.js v11.1.1](https://github.com/vercel/next.js/releases/tag/v11.1.1)

CVE-2021-39178 Affected Next Versions

1 component(s)
Fixed Versions:
11.1.1
Product / Package Ecosystem Affected Versions Fixed Version
next
npm/next
npm
≥ 10.0.0
< 11.1.1
11.1.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vercel/next.js/security/advisories/GHSA-9gr3-7897-pp7m
NVD — CVE-2021-39178 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-39178
Next Source Repository REPOSITORY
https://github.com/vercel/next.js/pull/28620
Security Fix Commit FIX COMMIT
https://github.com/vercel/next.js/commit/7afc97c5744b38bdf36aa7f87625f438224688aa
Next Source Repository REPOSITORY
https://github.com/vercel/next.js
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v11.1.1

Frequently Asked Questions

What is CVE-2021-39178?
CVE-2021-39178 is a security vulnerability in Next involving XSS in Image Optimization API for Next.js under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Next versions are affected?
Affected versions include releases prior to 11.1.1 across affected packages: next.
What version fixes CVE-2021-39178?
Upgrading to 11.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is next affected?
Yes, next is affected in releases prior to 11.1.1. Upgrade your dependency to 11.1.1 or later.
What is the CVSS score of CVE-2021-39178?
CVE-2021-39178 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-39178?
CVE-2021-39178 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-2021-39178?
Run the dependency tree command: 'npm ls next'. 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-9gr3-7897-pp7m",
  "modified" : "2021-08-31T20:01:51Z",
  "published" : "2021-09-01T18:24:22Z",
  "aliases" : [ "CVE-2021-39178" ],
  "summary" : "XSS in Image Optimization API for Next.js",
  "details" : "### Impact\n- **Affected:** All of the following must be true to be affected\n    - Next.js between version 10.0.0 and 11.1.0\n    - The `next.config.js` file has [`images.domains`](https://nextjs.org/docs/basic-features/image-optimization#domains) array assigned\n    - The image host assigned in [`images.domains`](https://nextjs.org/docs/basic-features/image-optimization#domains) allows user-provided SVG\n- **Not affected**: The `next.config.js` file has [`images.loader`](https://nextjs.org/docs/basic-features/image-optimization#loader) assigned to something other than default\n- **Not affected**: Deployments on [Vercel](https://vercel.com) are not affected\n\n### Patches\n[Next.js v11.1.1](https://github.com/vercel/next.js/releases/tag/v11.1.1)\n\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.0.0"
      }, {
        "fixed" : "11.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/security/advisories/GHSA-9gr3-7897-pp7m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-39178"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/pull/28620"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/commit/7afc97c5744b38bdf36aa7f87625f438224688aa"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vercel/next.js"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v11.1.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-31T20:01:51Z",
    "nvd_published_at" : "2021-08-31T00:15:00Z"
  }
}