CVE-2021-43787: Nodebb Cross-Site Scripting Vulnerability

CRITICAL
Advisory Identifier: GHSA-wx69-rvg3-x7fc
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CVSS 9.0
CWE-79
Published
Advisory Summary

CVE-2021-43787 is a CRITICAL (CVSS 9.0) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Nodebb libraries in the npm ecosystem. The issue involves xss via prototype pollution in nodebb. Remediation is available by upgrading affected packages to version 1.18.5.

CVE-2021-43787 at a Glance

CVE Identifier CVE-2021-43787
GHSA Identifier GHSA-wx69-rvg3-x7fc
Severity CRITICAL
CVSS v3.1 Base Score 9.0
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Nodebb
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 9.0

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-43787

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

nodebb fixed: 1.18.5 
npm install nodebb@1.18.5
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 nodebb

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-43787, inspect your project dependencies using npm:

npm ls nodebb

Analyze the terminal output to locate any version of Nodebb in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.18.5), your application is affected.

Note: The npm ls nodebb 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 Nodebb, 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 A prototype pollution vulnerability in the uploader module allowed a malicious user to inject arbitrary data (i.e. javascript) into the DOM, theoretically allowing for an account takeover when used in conjunction with a path traversal vulnerability disclosed at the same time as this report. ### Patches The vulnerability has been patched as of v1.18.5. ### Workarounds Cherry-pick commit hash 1783f918bc19568f421473824461ff2ed7755e4c to receive this patch in lieu of a full upgrade. ### For more information If you have any questions or comments about this advisory: * Email us at [security@nodebb.org](mailto:security@nodebb.org)

CVE-2021-43787 Affected Nodebb Versions

1 component(s)
Fixed Versions:
1.18.5
Product / Package Ecosystem Affected Versions Fixed Version
nodebb
npm/nodebb
npm
≥ 1.15.0
< 1.18.5
1.18.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/NodeBB/NodeBB/security/advisories/GHSA-wx69-rvg3-x7fc
NVD — CVE-2021-43787 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-43787
Security Fix Commit FIX COMMIT
https://github.com/NodeBB/NodeBB/commit/1783f918bc19568f421473824461ff2ed7755e4c
blog.sonarsource.com/nodebb-remote-code-... WEB
https://blog.sonarsource.com/nodebb-remote-code-execution-with-one-shot
Nodebb Source Repository REPOSITORY
https://github.com/NodeBB/NodeBB
Nodebb Release RELEASE
https://github.com/NodeBB/NodeBB/releases/tag/v1.18.5

Frequently Asked Questions

What is CVE-2021-43787?
CVE-2021-43787 is a security vulnerability in Nodebb involving XSS via prototype pollution in NodeBB under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Nodebb versions are affected?
Affected versions include releases prior to 1.18.5 across affected packages: nodebb.
What version fixes CVE-2021-43787?
Upgrading to 1.18.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is nodebb affected?
Yes, nodebb is affected in releases prior to 1.18.5. Upgrade your dependency to 1.18.5 or later.
What is the CVSS score of CVE-2021-43787?
CVE-2021-43787 has a CVSS v3.1 base score of 9.0 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H.
What CWE is associated with CVE-2021-43787?
CVE-2021-43787 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-2021-43787?
Run the dependency tree command: 'npm ls nodebb'. 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-wx69-rvg3-x7fc",
  "modified" : "2021-12-01T15:07:01Z",
  "published" : "2021-11-30T22:21:01Z",
  "aliases" : [ "CVE-2021-43787" ],
  "summary" : "XSS via prototype pollution in NodeBB ",
  "details" : "### Impact\nA prototype pollution vulnerability in the uploader module allowed a malicious user to inject arbitrary data (i.e. javascript) into the DOM, theoretically allowing for an account takeover when used in conjunction with a path traversal vulnerability disclosed at the same time as this report.\n\n### Patches\nThe vulnerability has been patched as of v1.18.5.\n\n### Workarounds\nCherry-pick commit hash 1783f918bc19568f421473824461ff2ed7755e4c to receive this patch in lieu of a full upgrade.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Email us at [security@nodebb.org](mailto:security@nodebb.org)\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "nodebb"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.15.0"
      }, {
        "fixed" : "1.18.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/NodeBB/NodeBB/security/advisories/GHSA-wx69-rvg3-x7fc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-43787"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NodeBB/NodeBB/commit/1783f918bc19568f421473824461ff2ed7755e4c"
  }, {
    "type" : "WEB",
    "url" : "https://blog.sonarsource.com/nodebb-remote-code-execution-with-one-shot"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/NodeBB/NodeBB"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NodeBB/NodeBB/releases/tag/v1.18.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-11-30T14:35:09Z",
    "nvd_published_at" : "2021-11-29T20:15:00Z"
  }
}