CVE-2026-4923: Path to regexp Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-27v5-c462-wpq7
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CVSS 5.9
CWE-1333
Published
Advisory Summary

CVE-2026-4923 is a MODERATE (CVSS 5.9) denial of service vulnerability (CWE-1333: Inefficient Regular Expression Complexity) affecting Path to regexp libraries in the npm ecosystem. The issue involves path-to-regexp vulnerable to regular expression denial of service via multiple wildcards. Remediation is available by upgrading affected packages to version 8.4.0.

CVE-2026-4923 at a Glance

CVE Identifier CVE-2026-4923
GHSA Identifier GHSA-27v5-c462-wpq7
Severity MODERATE
CVSS v3.1 Base Score 5.9
CWE Classification CWE-1333: Inefficient Regular Expression Complexity
Affected Product Path to regexp
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.9

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

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

How to Fix CVE-2026-4923

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

path-to-regexp fixed: 8.4.0 
npm install path-to-regexp@8.4.0
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 path-to-regexp

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-4923, inspect your project dependencies using npm:

npm ls path-to-regexp

Analyze the terminal output to locate any version of Path to regexp in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.4.0), your application is affected.

Note: The npm ls path-to-regexp 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 Path to regexp, 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

### Impact When using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the end of the path. **Unsafe examples:** ``` /*foo-*bar-:baz /*a-:b-*c-:d /x/*a-:b/*c/y ``` **Safe examples:** ``` /*foo-:bar /*foo-:bar-*baz ``` ### Patches Upgrade to version `8.4.0`. ### Workarounds If developers are using multiple wildcard parameters, they can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.

CVE-2026-4923 Affected Path to regexp Versions

1 component(s)
Fixed Versions:
8.4.0
Product / Package Ecosystem Affected Versions Fixed Version
path-to-regexp
npm/path-to-regexp
npm
≥ 8.0.0
< 8.4.0
8.4.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/pillarjs/path-to-regexp/security/advisories/GHSA-27v5-c462-wpq7
NVD — CVE-2026-4923 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4923
Path to regexp Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
Path to regexp Source Repository REPOSITORY
https://github.com/pillarjs/path-to-regexp
makenowjust-labs.github.io/recheck/playground WEB
https://makenowjust-labs.github.io/recheck/playground

Frequently Asked Questions

What is CVE-2026-4923?
CVE-2026-4923 is a security vulnerability in Path to regexp involving path-to-regexp vulnerable to Regular Expression Denial of Service via multiple wildcards under CWE-1333: Inefficient Regular Expression Complexity.
Which Path to regexp versions are affected?
Affected versions include releases prior to 8.4.0 across affected packages: path-to-regexp.
What version fixes CVE-2026-4923?
Upgrading to 8.4.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is path-to-regexp affected?
Yes, path-to-regexp is affected in releases prior to 8.4.0. Upgrade your dependency to 8.4.0 or later.
What is the CVSS score of CVE-2026-4923?
CVE-2026-4923 has a CVSS v3.1 base score of 5.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-4923?
CVE-2026-4923 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-2026-4923?
Run the dependency tree command: 'npm ls path-to-regexp'. 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-27v5-c462-wpq7",
  "modified" : "2026-03-27T22:23:52Z",
  "published" : "2026-03-27T22:23:52Z",
  "aliases" : [ "CVE-2026-4923" ],
  "summary" : "path-to-regexp vulnerable to Regular Expression Denial of Service via multiple wildcards",
  "details" : "### Impact\n\nWhen using multiple wildcards, combined with at least one parameter, a regular expression can be generated that is vulnerable to ReDoS. This backtracking vulnerability requires the second wildcard to be somewhere other than the end of the path.\n\n**Unsafe examples:**\n\n```\n/*foo-*bar-:baz\n/*a-:b-*c-:d\n/x/*a-:b/*c/y\n```\n\n**Safe examples:**\n\n```\n/*foo-:bar\n/*foo-:bar-*baz\n```\n\n### Patches\n\nUpgrade to version `8.4.0`.\n\n### Workarounds\n\nIf developers are using multiple wildcard parameters, they can check the regex output with a tool such as https://makenowjust-labs.github.io/recheck/playground/ to confirm whether a path is vulnerable.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "path-to-regexp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "8.0.0"
      }, {
        "fixed" : "8.4.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pillarjs/path-to-regexp/security/advisories/GHSA-27v5-c462-wpq7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4923"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pillarjs/path-to-regexp"
  }, {
    "type" : "WEB",
    "url" : "https://makenowjust-labs.github.io/recheck/playground"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-27T22:23:52Z",
    "nvd_published_at" : "2026-03-26T19:17:08Z"
  }
}