CVE-2021-23387: Trailing slash Open Redirect Vulnerability

MODERATE
Advisory Identifier: GHSA-rfhr-62xp-2fp2
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CVSS 5.4
CWE-601
Published
Advisory Summary

CVE-2021-23387 is a MODERATE (CVSS 5.4) open redirect vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Trailing slash libraries in the npm ecosystem. The issue involves open redirect in trailing-slash. Remediation is available by upgrading affected packages to version 2.0.1.

CVE-2021-23387 at a Glance

CVE Identifier CVE-2021-23387
GHSA Identifier GHSA-rfhr-62xp-2fp2
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Trailing slash
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.4

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

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

How to Fix CVE-2021-23387

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

trailing-slash fixed: 2.0.1 
npm install trailing-slash@2.0.1
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 trailing-slash

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-23387, inspect your project dependencies using npm:

npm ls trailing-slash

Analyze the terminal output to locate any version of Trailing slash in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.0.1), your application is affected.

Note: The npm ls trailing-slash 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-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Trailing slash, 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

The package trailing-slash before 2.0.1 are vulnerable to Open Redirect via the use of trailing double slashes in the URL when accessing the vulnerable endpoint (such as https://example.com//attacker.example/). The vulnerable code is in index.js::createTrailing(), as the web server uses relative URLs instead of absolute URLs.

CVE-2021-23387 Affected Trailing slash Versions

1 component(s)
Fixed Versions:
2.0.1
Product / Package Ecosystem Affected Versions Fixed Version
trailing-slash
npm/trailing-slash
npm
< 2.0.1
2.0.1

References

NVD — CVE-2021-23387 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23387
Security Fix Commit FIX COMMIT
https://github.com/fardog/trailing-slash/commit/f8e66f1429308247e5a119d430203077d8f05048
Trailing slash Source Repository REPOSITORY
https://github.com/fardog/trailing-slash/blob/f640ece055fe85275c983de5eb94661b95e35670/index.js%23L36
snyk.io/vuln/snyk-js-traili... WEB
https://snyk.io/vuln/SNYK-JS-TRAILINGSLASH-1085707

Frequently Asked Questions

What is CVE-2021-23387?
CVE-2021-23387 is a security vulnerability in Trailing slash involving Open Redirect in trailing-slash under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Trailing slash versions are affected?
Affected versions include releases prior to 2.0.1 across affected packages: trailing-slash.
What version fixes CVE-2021-23387?
Upgrading to 2.0.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is trailing-slash affected?
Yes, trailing-slash is affected in releases prior to 2.0.1. Upgrade your dependency to 2.0.1 or later.
What is the CVSS score of CVE-2021-23387?
CVE-2021-23387 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2021-23387?
CVE-2021-23387 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check npm dependencies for CVE-2021-23387?
Run the dependency tree command: 'npm ls trailing-slash'. 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-rfhr-62xp-2fp2",
  "modified" : "2021-05-27T22:38:20Z",
  "published" : "2021-06-08T23:19:21Z",
  "aliases" : [ "CVE-2021-23387" ],
  "summary" : "Open Redirect in trailing-slash",
  "details" : "The package trailing-slash before 2.0.1 are vulnerable to Open Redirect via the use of trailing double slashes in the URL when accessing the vulnerable endpoint (such as https://example.com//attacker.example/). The vulnerable code is in index.js::createTrailing(), as the web server uses relative URLs instead of absolute URLs.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "trailing-slash"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23387"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fardog/trailing-slash/commit/f8e66f1429308247e5a119d430203077d8f05048"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fardog/trailing-slash/blob/f640ece055fe85275c983de5eb94661b95e35670/index.js%23L36"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-TRAILINGSLASH-1085707"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-27T22:38:20Z",
    "nvd_published_at" : "2021-05-24T19:15:00Z"
  }
}