CVE-2018-20583: League/commonmark Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-qx76-c53f-5c7q
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CVSS 6.1
CWE-79
Published
Advisory Summary

CVE-2018-20583 is a MODERATE (CVSS 6.1) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting League/commonmark libraries in the Packagist ecosystem. The issue involves php league commonmark vulnerable to cross-site scripting (xss). Remediation is available by upgrading affected packages to version 0.18.1.

CVE-2018-20583 at a Glance

CVE Identifier CVE-2018-20583
GHSA Identifier GHSA-qx76-c53f-5c7q
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product League/commonmark
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 6.1

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:R/S:C/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 Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2018-20583

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

league/commonmark fixed: 0.18.1 
Upgrade league/commonmark to 0.18.1
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 league/commonmark

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-20583, inspect your project dependencies for League/commonmark:

inspect dependencies for league/commonmark

Analyze the terminal output to locate any version of League/commonmark in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.18.1), 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 League/commonmark, 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

Cross-site scripting (XSS) vulnerability in the PHP League CommonMark library versions 0.15.6 through 0.18.x before 0.18.1 allows remote attackers to insert unsafe URLs into HTML (even if allow_unsafe_links is false) via a newline character (e.g., writing javascript as javascri%0apt).

CVE-2018-20583 Affected League/commonmark Versions

1 component(s)
Fixed Versions:
0.18.1
Product / Package Ecosystem Affected Versions Fixed Version
league/commonmark
 Packagist
≥ 0.15.6
< 0.18.1
0.18.1

References

NVD — CVE-2018-20583 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20583
League/commonmark Source Repository REPOSITORY
https://github.com/thephpleague/commonmark/issues/337
commonmark.thephpleague.com/changelog WEB
https://commonmark.thephpleague.com/changelog
League/commonmark Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/league/commonmark/CVE-2018-20583.yaml
League/commonmark Source Repository REPOSITORY
https://github.com/thephpleague/commonmark
League/commonmark Release RELEASE
https://github.com/thephpleague/commonmark/releases/tag/0.18.1

Frequently Asked Questions

What is CVE-2018-20583?
CVE-2018-20583 is a security vulnerability in League/commonmark involving PHP League CommonMark vulnerable to Cross-Site Scripting (XSS) under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which League/commonmark versions are affected?
Affected versions include releases prior to 0.18.1 across affected packages: league/commonmark.
What version fixes CVE-2018-20583?
Upgrading to 0.18.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is league/commonmark affected?
Yes, league/commonmark is affected in releases prior to 0.18.1. Upgrade your dependency to 0.18.1 or later.
What is the CVSS score of CVE-2018-20583?
CVE-2018-20583 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2018-20583?
CVE-2018-20583 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-2018-20583?
Run the dependency tree command: 'inspect dependencies for league/commonmark'. 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-qx76-c53f-5c7q",
  "modified" : "2022-09-12T15:59:43Z",
  "published" : "2022-05-14T01:40:50Z",
  "aliases" : [ "CVE-2018-20583" ],
  "summary" : "PHP League CommonMark vulnerable to Cross-Site Scripting (XSS)",
  "details" : "Cross-site scripting (XSS) vulnerability in the PHP League CommonMark library versions 0.15.6 through 0.18.x before 0.18.1 allows remote attackers to insert unsafe URLs into HTML (even if allow_unsafe_links is false) via a newline character (e.g., writing javascript as javascri%0apt).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "league/commonmark"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.15.6"
      }, {
        "fixed" : "0.18.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20583"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/thephpleague/commonmark/issues/337"
  }, {
    "type" : "WEB",
    "url" : "https://commonmark.thephpleague.com/changelog"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/league/commonmark/CVE-2018-20583.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/thephpleague/commonmark"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/thephpleague/commonmark/releases/tag/0.18.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-09-12T15:59:43Z",
    "nvd_published_at" : "2018-12-30T05:29:00Z"
  }
}