CVE-2020-7777: Jsen Code Injection Vulnerability

HIGH
Advisory Identifier: GHSA-vm64-cfqx-3698
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CVSS 7.2
CWE-94
Published
Advisory Summary

CVE-2020-7777 is a HIGH (CVSS 7.2) code injection vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Jsen libraries in the npm ecosystem. The issue involves code injection in jsen. Remediation is available in the latest vendor maintenance releases.

CVE-2020-7777 at a Glance

CVE Identifier CVE-2020-7777
GHSA Identifier GHSA-vm64-cfqx-3698
Severity HIGH
CVSS v3.1 Base Score 7.2
CWE Classification CWE-94: Improper Control of Generation of Code ('Code Injection')
Affected Product Jsen
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.2

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

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

How to Fix CVE-2020-7777

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

jsen fixed: Latest secure release 
npm install jsen@Latest secure release
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 jsen

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2020-7777, inspect your project dependencies using npm:

npm ls jsen

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

Note: The npm ls jsen 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-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. In Jsen, 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

This affects all versions of package jsen. If an attacker can control the schema file, it could run arbitrary JavaScript code on the victim machine. In the module description and README file there is no mention about the risks of untrusted schema files, so it is assumed that this is applicable. In particular the required field of the schema is not properly sanitized. The resulting string that is build based on the schema definition is then passed to a `Function.apply();`, leading to an Arbitrary Code Execution. ### PoC ```js const jsen = require('jsen'); let schema = JSON.parse( { "type": "object", "properties": { "username": { "type": "string" } }, "required": ["\\"+process.mainModule.require(\'child_process\').execSync(\'touch malicious\')+\\""] } ); const validate = jsen(schema); validate({}); ```

CVE-2020-7777 Affected Jsen Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
jsen
npm/jsen
npm
≤ 0.6.6

References

NVD — CVE-2020-7777 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-7777
Jsen Source Repository REPOSITORY
https://github.com/bugventure/jsen/blob/master/lib/jsen.js#L875
Jsen Security Information SECURITY
https://security.snyk.io/vuln/SNYK-JS-JSEN-1014670

Frequently Asked Questions

What is CVE-2020-7777?
CVE-2020-7777 is a security vulnerability in Jsen involving Code Injection in jsen under CWE-94: Improper Control of Generation of Code ('Code Injection').
Which Jsen versions are affected?
Affected versions include releases prior to current release patches across affected packages: jsen.
What version fixes CVE-2020-7777?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is jsen affected?
Yes, jsen is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2020-7777?
CVE-2020-7777 has a CVSS v3.1 base score of 7.2 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2020-7777?
CVE-2020-7777 is classified under CWE-94: Improper Control of Generation of Code ('Code Injection') (The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.).
How can I check npm dependencies for CVE-2020-7777?
Run the dependency tree command: 'npm ls jsen'. 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-vm64-cfqx-3698",
  "modified" : "2023-09-11T23:08:53Z",
  "published" : "2022-02-10T20:18:37Z",
  "aliases" : [ "CVE-2020-7777" ],
  "summary" : "Code Injection in jsen",
  "details" : "This affects all versions of package jsen. If an attacker can control the schema file, it could run arbitrary JavaScript code on the victim machine. In the module description and README file there is no mention about the risks of untrusted schema files, so it is assumed that this is applicable. In particular the required field of the schema is not properly sanitized. The resulting string that is build based on the schema definition is then passed to a `Function.apply();`, leading to an Arbitrary Code Execution.\n\n### PoC\n```js\nconst jsen = require('jsen');\nlet schema = JSON.parse(\n{ "type": "object", "properties": { "username": { "type": "string" } }, "required": ["\\\\"+process.mainModule.require(\\'child_process\\').execSync(\\'touch malicious\\')+\\\\""] }\n);\n\nconst validate = jsen(schema); validate({});\n```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "jsen"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.6.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-7777"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bugventure/jsen/blob/master/lib/jsen.js#L875"
  }, {
    "type" : "WEB",
    "url" : "https://security.snyk.io/vuln/SNYK-JS-JSEN-1014670"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-14T19:49:04Z",
    "nvd_published_at" : "2020-11-23T16:15:00Z"
  }
}