CVE-2021-3783: Yourls/yourls Cross-Site Scripting Vulnerability

MODERATE

Advisory Identifier: GHSA-cpq8-x35g-m439

CVSS 6.6

Published 2021-09-20

Advisory Summary

CVE-2021-3783 is a MODERATE (CVSS 6.6) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Yourls/yourls libraries in the Packagist ecosystem. The issue involves cross-site scripting in yourls. Remediation is available in the latest vendor maintenance releases.

CVE-2021-3783 at a Glance

CVE Identifier CVE-2021-3783

GHSA Identifier GHSA-cpq8-x35g-m439

Severity MODERATE

CVSS v3.1 Base Score 6.6

CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Product Yourls/yourls

Package Ecosystem Packagist

Published Date 2021-09-20

Last Updated 2021-09-16

Security Impact

CVSS: 6.6

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)

Attack Complexity High (AC:H)

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-2021-3783

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

yourls/yourls fixed: Latest secure release

Upgrade yourls/yourls to 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:

inspect dependencies for yourls/yourls

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-3783, inspect your project dependencies for Yourls/yourls:

inspect dependencies for yourls/yourls

Analyze the terminal output to locate any version of Yourls/yourls 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: Verify declared build manifests and deployed runtime container environments.

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 Yourls/yourls, 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

yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in arbitrary path handling.

CVE-2021-3783 Affected Yourls/yourls Versions

1 component(s)

Product / Package	Ecosystem	Affected Versions	Fixed Version
yourls/yourls	Packagist	≤ 1.8.2

References

NVD — CVE-2021-3783 NVD

https://nvd.nist.gov/vuln/detail/CVE-2021-3783

Security Fix Commit FIX COMMIT

https://github.com/yourls/yourls/commit/94f6bab91182142c96ff11f481585b445449efd4

Yourls/yourls Source Repository REPOSITORY

https://github.com/yourls/yourls

huntr.dev/bounties/b688e553-d... WEB

https://huntr.dev/bounties/b688e553-d0d9-4ddf-95a3-ff4b78004984

Frequently Asked Questions

What is CVE-2021-3783?

CVE-2021-3783 is a security vulnerability in Yourls/yourls involving Cross-site Scripting in yourls under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').

Which Yourls/yourls versions are affected?

Affected versions include releases prior to current release patches across affected packages: yourls/yourls.

What version fixes CVE-2021-3783?

Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.

Is yourls/yourls affected?

Yes, yourls/yourls 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-2021-3783?

CVE-2021-3783 has a CVSS v3.1 base score of 6.6 (MODERATE) with vector string CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H.

What CWE is associated with CVE-2021-3783?

CVE-2021-3783 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 Packagist dependencies for CVE-2021-3783?

Run the dependency tree command: 'inspect dependencies for yourls/yourls'. 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-cpq8-x35g-m439",
  "modified" : "2021-09-16T18:19:29Z",
  "published" : "2021-09-20T20:43:15Z",
  "aliases" : [ "CVE-2021-3783" ],
  "summary" : "Cross-site Scripting in yourls",
  "details" : "yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in arbitrary path handling.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "yourls/yourls"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.8.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3783"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yourls/yourls/commit/94f6bab91182142c96ff11f481585b445449efd4"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/yourls/yourls"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.dev/bounties/b688e553-d0d9-4ddf-95a3-ff4b78004984"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-16T18:19:29Z",
    "nvd_published_at" : "2021-09-15T12:15:00Z"
  }
}

CVSS V3

6.6 MODERATE