CVE-2026-1528: Undici Malicious WebSocket 64-bit Length Overflows Vulnerability

HIGH
Advisory Identifier: GHSA-f269-vfmq-vjvj
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CVSS 7.5
CWE-1284 CWE-248
Published
Advisory Summary

CVE-2026-1528 is a HIGH (CVSS 7.5) malicious websocket 64-bit length overflows vulnerability (CWE-1284: Improper Validation of Specified Quantity in Input) affecting Undici libraries in the npm ecosystem. The issue involves malicious websocket 64-bit length overflows parser and crashes the client. Remediation is available by upgrading affected packages to version 6.24.0, 7.24.0.

CVE-2026-1528 at a Glance

CVE Identifier CVE-2026-1528
GHSA Identifier GHSA-f269-vfmq-vjvj
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-1284: Improper Validation of Specified Quantity in Input
Affected Product Undici
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:H).

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 High (A:H)

How to Fix CVE-2026-1528

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

undici fixed: 6.24.0 
npm install undici@6.24.0
undici fixed: 7.24.0 
npm install undici@7.24.0
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 undici

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-1528, inspect your project dependencies using npm:

npm ls undici

Analyze the terminal output to locate any version of Undici in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.24.0), your application is affected.

Note: The npm ls undici 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-1284: Improper Validation of Specified Quantity in Input, where the product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. In Undici, 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 A server can reply with a WebSocket frame using the 64-bit length form and an extremely large length. undici's ByteParser overflows internal math, ends up in an invalid state, and throws a fatal TypeError that terminates the process. ### Patches Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later. ### Workarounds There are no workarounds.

CVE-2026-1528 Affected Undici Versions

2 component(s)
Fixed Versions:
6.24.07.24.0
Product / Package Ecosystem Affected Versions Fixed Version
undici
npm/undici
npm
≥ 6.0.0
< 6.24.0
6.24.0
undici
npm/undici
npm
≥ 7.0.0
< 7.24.0
7.24.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nodejs/undici/security/advisories/GHSA-f269-vfmq-vjvj
NVD — CVE-2026-1528 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-1528
hackerone.com/reports/3537648 WEB
https://hackerone.com/reports/3537648
Undici Security Information SECURITY
https://cna.openjsf.org/security-advisories.html
Undici Source Repository REPOSITORY
https://github.com/nodejs/undici

Frequently Asked Questions

What is CVE-2026-1528?
CVE-2026-1528 is a security vulnerability in Undici involving Malicious WebSocket 64-bit length overflows parser and crashes the client under CWE-1284: Improper Validation of Specified Quantity in Input.
Which Undici versions are affected?
Affected versions include releases prior to 6.24.0, 7.24.0 across affected packages: undici.
What version fixes CVE-2026-1528?
Upgrading to 6.24.0, 7.24.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is undici affected?
Yes, undici is affected in releases prior to 6.24.0, 7.24.0. Upgrade your dependency to 6.24.0, 7.24.0 or later.
What is the CVSS score of CVE-2026-1528?
CVE-2026-1528 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-1528?
CVE-2026-1528 is classified under CWE-1284: Improper Validation of Specified Quantity in Input (The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.).
How can I check npm dependencies for CVE-2026-1528?
Run the dependency tree command: 'npm ls undici'. 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-f269-vfmq-vjvj",
  "modified" : "2026-03-13T20:07:26Z",
  "published" : "2026-03-13T20:07:26Z",
  "aliases" : [ "CVE-2026-1528" ],
  "summary" : "Undici: Malicious WebSocket 64-bit length overflows parser and crashes the client",
  "details" : "### Impact\nA server can reply with a WebSocket frame using the 64-bit length form and an extremely large length. undici's ByteParser overflows internal math, ends up in an invalid state, and throws a fatal TypeError that terminates the process. \n\n### Patches\n\n\n Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.\n\n### Workarounds\n\nThere are no workarounds.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "undici"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.0.0"
      }, {
        "fixed" : "6.24.0"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "undici"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.0.0"
      }, {
        "fixed" : "7.24.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nodejs/undici/security/advisories/GHSA-f269-vfmq-vjvj"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-1528"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/3537648"
  }, {
    "type" : "WEB",
    "url" : "https://cna.openjsf.org/security-advisories.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nodejs/undici"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1284", "CWE-248" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-13T20:07:26Z",
    "nvd_published_at" : "2026-03-12T21:16:25Z"
  }
}