CVE-2026-2327: Markdown it Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-38c4-r59v-3vqw
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CVSS 5.3
CWE-1333
Published
Advisory Summary

CVE-2026-2327 is a MODERATE (CVSS 5.3) denial of service vulnerability (CWE-1333: Inefficient Regular Expression Complexity) affecting Markdown it libraries in the npm ecosystem. The issue involves markdown-it is has a regular expression denial of service (redos). Remediation is available by upgrading affected packages to version 14.1.1.

CVE-2026-2327 at a Glance

CVE Identifier CVE-2026-2327
GHSA Identifier GHSA-38c4-r59v-3vqw
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-1333: Inefficient Regular Expression Complexity
Affected Product Markdown it
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:N/S:U/C:N/I:N/A:L).

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 Low (A:L)

How to Fix CVE-2026-2327

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

markdown-it fixed: 14.1.1 
npm install markdown-it@14.1.1
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 markdown-it

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-2327, inspect your project dependencies using npm:

npm ls markdown-it

Analyze the terminal output to locate any version of Markdown it in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 14.1.1), your application is affected.

Note: The npm ls markdown-it 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-1333: Inefficient Regular Expression Complexity, where the product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential. In Markdown it, 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

Versions of the package markdown-it from 13.0.0 and before 14.1.1 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the use of the regex /\*+$/ in the linkify function. An attacker can supply a long sequence of * characters followed by a non-matching character, which triggers excessive backtracking and may lead to a denial-of-service condition.

CVE-2026-2327 Affected Markdown it Versions

1 component(s)
Fixed Versions:
14.1.1
Product / Package Ecosystem Affected Versions Fixed Version
markdown-it
npm/markdown-it
npm
≥ 13.0.0
< 14.1.1
14.1.1

References

NVD — CVE-2026-2327 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2327
Security Fix Commit FIX COMMIT
https://github.com/markdown-it/markdown-it/commit/4b4bbcae5e0990a5b172378e507b33a59012ed26
Markdown it Source Repository REPOSITORY
https://gist.github.com/ltduc147/c9abecae1b291ede4f692f2ab988c917
Markdown it Source Repository REPOSITORY
https://github.com/markdown-it/markdown-it
Markdown it Source Repository REPOSITORY
https://github.com/markdown-it/markdown-it/blob/14.1.0/lib/rules_inline/linkify.mjs#L33
Markdown it Security Information SECURITY
https://security.snyk.io/vuln/SNYK-JS-MARKDOWNIT-10666750

Frequently Asked Questions

What is CVE-2026-2327?
CVE-2026-2327 is a security vulnerability in Markdown it involving markdown-it is has a Regular Expression Denial of Service (ReDoS) under CWE-1333: Inefficient Regular Expression Complexity.
Which Markdown it versions are affected?
Affected versions include releases prior to 14.1.1 across affected packages: markdown-it.
What version fixes CVE-2026-2327?
Upgrading to 14.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is markdown-it affected?
Yes, markdown-it is affected in releases prior to 14.1.1. Upgrade your dependency to 14.1.1 or later.
What is the CVSS score of CVE-2026-2327?
CVE-2026-2327 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-2327?
CVE-2026-2327 is classified under CWE-1333: Inefficient Regular Expression Complexity (The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.).
How can I check npm dependencies for CVE-2026-2327?
Run the dependency tree command: 'npm ls markdown-it'. 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-38c4-r59v-3vqw",
  "modified" : "2026-02-13T20:04:39Z",
  "published" : "2026-02-12T06:30:13Z",
  "aliases" : [ "CVE-2026-2327" ],
  "summary" : "markdown-it is has a Regular Expression Denial of Service (ReDoS)",
  "details" : "Versions of the package markdown-it from 13.0.0 and before 14.1.1 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the use of the regex /\\*+$/ in the linkify function. An attacker can supply a long sequence of * characters followed by a non-matching character, which triggers excessive backtracking and may lead to a denial-of-service condition.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "markdown-it"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "13.0.0"
      }, {
        "fixed" : "14.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2327"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/markdown-it/markdown-it/commit/4b4bbcae5e0990a5b172378e507b33a59012ed26"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/ltduc147/c9abecae1b291ede4f692f2ab988c917"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/markdown-it/markdown-it"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/markdown-it/markdown-it/blob/14.1.0/lib/rules_inline/linkify.mjs#L33"
  }, {
    "type" : "WEB",
    "url" : "https://security.snyk.io/vuln/SNYK-JS-MARKDOWNIT-10666750"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-13T20:04:39Z",
    "nvd_published_at" : "2026-02-12T06:16:02Z"
  }
}