CVE-2021-3795: Semver regex Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-44c6-4v22-4mhx
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CVSS 7.5
CWE-400 CWE-1333
Published
Advisory Summary

CVE-2021-3795 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Semver regex libraries in the npm ecosystem. The issue involves semver-regex regular expression denial of service (redos). Remediation is available by upgrading affected packages to version 3.1.3, 4.0.1.

CVE-2021-3795 at a Glance

CVE Identifier CVE-2021-3795
GHSA Identifier GHSA-44c6-4v22-4mhx
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Semver regex
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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

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

How to Fix CVE-2021-3795

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

semver-regex fixed: 3.1.3 
npm install semver-regex@3.1.3
semver-regex fixed: 4.0.1 
npm install semver-regex@4.0.1
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 semver-regex

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-3795, inspect your project dependencies using npm:

npm ls semver-regex

Analyze the terminal output to locate any version of Semver regex in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.1.3), your application is affected.

Note: The npm ls semver-regex 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Semver regex, 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

npm `semver-regex` is vulnerable to Inefficient Regular Expression Complexity

CVE-2021-3795 Affected Semver regex Versions

2 component(s)
Fixed Versions:
3.1.34.0.1
Product / Package Ecosystem Affected Versions Fixed Version
semver-regex
npm/semver-regex
npm
< 3.1.3
3.1.3
semver-regex
npm/semver-regex
npm
≥ 4.0.0
< 4.0.1
All 1 versions
4.0.0
4.0.1

References

NVD — CVE-2021-3795 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3795
Security Fix Commit FIX COMMIT
https://github.com/sindresorhus/semver-regex/commit/11c66245f4e1976dccc52977ed183696a21a3fd7
Semver regex Source Repository REPOSITORY
https://github.com/sindresorhus/semver-regex
huntr.dev/bounties/006624e3-3... WEB
https://huntr.dev/bounties/006624e3-35ac-448f-aab9-7b5183f30e28

Frequently Asked Questions

What is CVE-2021-3795?
CVE-2021-3795 is a security vulnerability in Semver regex involving semver-regex Regular Expression Denial of Service (ReDOS) under CWE-400: Uncontrolled Resource Consumption.
Which Semver regex versions are affected?
Affected versions include releases prior to 3.1.3, 4.0.1 across affected packages: semver-regex.
What version fixes CVE-2021-3795?
Upgrading to 3.1.3, 4.0.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is semver-regex affected?
Yes, semver-regex is affected in releases prior to 3.1.3, 4.0.1. Upgrade your dependency to 3.1.3, 4.0.1 or later.
What is the CVSS score of CVE-2021-3795?
CVE-2021-3795 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-3795?
CVE-2021-3795 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check npm dependencies for CVE-2021-3795?
Run the dependency tree command: 'npm ls semver-regex'. 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-44c6-4v22-4mhx",
  "modified" : "2023-07-11T13:37:50Z",
  "published" : "2021-09-20T20:42:25Z",
  "aliases" : [ "CVE-2021-3795" ],
  "summary" : "semver-regex Regular Expression Denial of Service (ReDOS)",
  "details" : "npm `semver-regex` is vulnerable to Inefficient Regular Expression Complexity",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "semver-regex"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.1.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "semver-regex"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.1"
      } ]
    } ],
    "versions" : [ "4.0.0" ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3795"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sindresorhus/semver-regex/commit/11c66245f4e1976dccc52977ed183696a21a3fd7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sindresorhus/semver-regex"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.dev/bounties/006624e3-35ac-448f-aab9-7b5183f30e28"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333", "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-16T17:31:51Z",
    "nvd_published_at" : "2021-09-15T17:15:00Z"
  }
}