CVE-2021-3785: Yourls/yourls Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-m9fq-c9hp-59g7
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CVSS 5.4
CWE-79
Published
Advisory Summary

CVE-2021-3785 is a MODERATE (CVSS 5.4) 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 by upgrading affected packages to version 1.8.2.

CVE-2021-3785 at a Glance

CVE Identifier CVE-2021-3785
GHSA Identifier GHSA-m9fq-c9hp-59g7
Severity MODERATE
CVSS v3.1 Base Score 5.4
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Yourls/yourls
Package Ecosystem Packagist
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:L/UI:R/S:C/C:L/I:L/A:N).

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

How to Fix CVE-2021-3785

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: 1.8.2 
Upgrade yourls/yourls to 1.8.2
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-2021-3785, 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 1.8.2), 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 edit dialog.

CVE-2021-3785 Affected Yourls/yourls Versions

1 component(s)
Fixed Versions:
1.8.2
Product / Package Ecosystem Affected Versions Fixed Version
yourls/yourls
 Packagist
< 1.8.2
1.8.2

References

NVD — CVE-2021-3785 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3785
Security Fix Commit FIX COMMIT
https://github.com/yourls/yourls/commit/1d8e224ebabb8a4c75b97f026950ed710faab0ff
Yourls/yourls Source Repository REPOSITORY
https://github.com/yourls/yourls
huntr.dev/bounties/b4085d13-5... WEB
https://huntr.dev/bounties/b4085d13-54fa-4419-a2ce-1d780cc31638

Frequently Asked Questions

What is CVE-2021-3785?
CVE-2021-3785 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 1.8.2 across affected packages: yourls/yourls.
What version fixes CVE-2021-3785?
Upgrading to 1.8.2 (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 1.8.2. Upgrade your dependency to 1.8.2 or later.
What is the CVSS score of CVE-2021-3785?
CVE-2021-3785 has a CVSS v3.1 base score of 5.4 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2021-3785?
CVE-2021-3785 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-2021-3785?
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-m9fq-c9hp-59g7",
  "modified" : "2021-09-24T13:08:49Z",
  "published" : "2021-09-20T20:42:52Z",
  "aliases" : [ "CVE-2021-3785" ],
  "summary" : "Cross-site Scripting in yourls",
  "details" : "yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in edit dialog.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "yourls/yourls"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.8.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3785"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yourls/yourls/commit/1d8e224ebabb8a4c75b97f026950ed710faab0ff"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/yourls/yourls"
  }, {
    "type" : "WEB",
    "url" : "https://huntr.dev/bounties/b4085d13-54fa-4419-a2ce-1d780cc31638"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-09-16T18:18:05Z",
    "nvd_published_at" : "2021-09-15T12:15:00Z"
  }
}