CVE-2021-27884: Yapi vendor Weak JSON Web Token Vulnerability

MODERATE
Advisory Identifier: GHSA-2h3h-vw8r-82rp
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CVSS 5.1
CWE-330
Published
Advisory Summary

CVE-2021-27884 is a MODERATE (CVSS 5.1) weak json web token vulnerability (CWE-330: Use of Insufficiently Random Values) affecting Yapi vendor libraries in the npm ecosystem. The issue involves weak json web token in yapi-vendor. Remediation is available by upgrading affected packages to version 1.9.3.

CVE-2021-27884 at a Glance

CVE Identifier CVE-2021-27884
GHSA Identifier GHSA-2h3h-vw8r-82rp
Severity MODERATE
CVSS v3.1 Base Score 5.1
CWE Classification CWE-330: Use of Insufficiently Random Values
Affected Product Yapi vendor
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.1

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

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

How to Fix CVE-2021-27884

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

yapi-vendor fixed: 1.9.3 
npm install yapi-vendor@1.9.3
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 yapi-vendor

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-27884, inspect your project dependencies using npm:

npm ls yapi-vendor

Analyze the terminal output to locate any version of Yapi vendor in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.9.3), your application is affected.

Note: The npm ls yapi-vendor 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-330: Use of Insufficiently Random Values, where the product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. In Yapi vendor, 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

Weak JSON Web Token (JWT) signing secret generation in YMFE YApi through 1.9.2 allows recreation of other users' JWT tokens. This occurs because Math.random in Node.js is used as a source of randomness in jwt signing. Math.random does not provide cryptographically secure random numbers. This has been patched in version 1.9.3.

CVE-2021-27884 Affected Yapi vendor Versions

1 component(s)
Fixed Versions:
1.9.3
Product / Package Ecosystem Affected Versions Fixed Version
yapi-vendor
npm/yapi-vendor
npm
< 1.9.3
1.9.3

References

NVD — CVE-2021-27884 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-27884
Yapi vendor Source Repository REPOSITORY
https://github.com/YMFE/yapi/issues/2117
Yapi vendor Source Repository REPOSITORY
https://github.com/YMFE/yapi/issues/2263
GitHub Advisory / Wiki ADVISORY
https://securitylab.github.com/advisories/GHSL-2020-228-YMFE-yapi

Frequently Asked Questions

What is CVE-2021-27884?
CVE-2021-27884 is a security vulnerability in Yapi vendor involving Weak JSON Web Token in yapi-vendor under CWE-330: Use of Insufficiently Random Values.
Which Yapi vendor versions are affected?
Affected versions include releases prior to 1.9.3 across affected packages: yapi-vendor.
What version fixes CVE-2021-27884?
Upgrading to 1.9.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is yapi-vendor affected?
Yes, yapi-vendor is affected in releases prior to 1.9.3. Upgrade your dependency to 1.9.3 or later.
What is the CVSS score of CVE-2021-27884?
CVE-2021-27884 has a CVSS v3.1 base score of 5.1 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2021-27884?
CVE-2021-27884 is classified under CWE-330: Use of Insufficiently Random Values (The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.).
How can I check npm dependencies for CVE-2021-27884?
Run the dependency tree command: 'npm ls yapi-vendor'. 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-2h3h-vw8r-82rp",
  "modified" : "2021-07-22T15:58:18Z",
  "published" : "2021-03-26T16:49:26Z",
  "aliases" : [ "CVE-2021-27884" ],
  "summary" : "Weak JSON Web Token in yapi-vendor",
  "details" : "Weak JSON Web Token (JWT) signing secret generation in YMFE YApi through 1.9.2 allows recreation of other users' JWT tokens. This occurs because Math.random in Node.js is used as a source of randomness in jwt signing. Math.random does not provide cryptographically secure random numbers. This has been patched in version 1.9.3.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "yapi-vendor"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.9.2"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-27884"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/YMFE/yapi/issues/2117"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/YMFE/yapi/issues/2263"
  }, {
    "type" : "ADVISORY",
    "url" : "https://securitylab.github.com/advisories/GHSL-2020-228-YMFE-yapi"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-330" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-26T16:48:44Z",
    "nvd_published_at" : "2021-03-01T23:15:00Z"
  }
}