# CVE-2026-1528: Node.js undici denial of service via WebSocket length overflow

Source: https://junglewise.ai/threats/cve-2026-1528-node-js-undici-denial-of-service-via-websocket-length-overflow  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-12. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-1528 · Severity: high · CVSS 7.5 · Published 2026-03-12

Undici is a popular HTTP and WebSocket client for Node.js used to fetch data and maintain real-time connections. A vulnerability in its WebSocket implementation allows a malicious server to crash the client application by sending a specially crafted message with an extremely large length value. This results in a denial-of-service (DoS) condition, potentially disrupting services that rely on Undici for external communications.

Technologies: [undici (npm)](https://junglewise.ai/threats/technologies/undici). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-1528 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-1528 being exploited in the wild.

**How severe is CVE-2026-1528?** High severity, with a CVSS score of 7.5, published 12 March 2026.

**Which products and versions are affected?** undici (npm) SEMVER:introduced=6.0.0,fixed=6.24.0.

**Is there a fix for CVE-2026-1528?** Yes. undici (npm): upgrade to 6.24.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-1528 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-1528?** Check whether you run undici (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- undici (npm): upgrade to 6.24.0 or later

  ```sh
  npm install undici@6.24.0
  ```


## Technical details

A vulnerability exists in the Undici WebSocket client's ByteParser component. When a server responds with a WebSocket frame using the 64-bit length form containing an extremely large value, the internal mathematical operations in ByteParser overflow. This causes the parser to enter an invalid state and throw an uncaught TypeError. Because this exception is fatal, it terminates the Node.js process. The issue is classified under CWE-1284 (Improper Validation of Specified Quantity in Input) and CWE-248 (Uncaught Exception). It is fixed in versions 7.24.0 and 6.24.0.

## Affected products

- Node.js undici < 6.24.0, < 7.24.0

## Identifiers

- CVE-2026-1528
- GHSA-f269-vfmq-vjvj

## Timeline

- 2026-03-12: disclosed
- 2026-03-12: advisory
- 2026-03-12: patched

## References

- [https://github.com/nodejs/undici/](https://github.com/nodejs/undici/)
- [https://cna.openjsf.org/security-advisories.html](https://cna.openjsf.org/security-advisories.html)
- [https://github.com/nodejs/undici/security/advisories/GHSA-f269-vfmq-vjvj](https://github.com/nodejs/undici/security/advisories/GHSA-f269-vfmq-vjvj)
- [https://hackerone.com/reports/3537648](https://hackerone.com/reports/3537648)
- [https://access.redhat.com/errata/RHSA-2026:13826](https://access.redhat.com/errata/RHSA-2026:13826)
- [https://access.redhat.com/errata/RHSA-2026:17789](https://access.redhat.com/errata/RHSA-2026:17789)
- [https://access.redhat.com/errata/RHSA-2026:21772](https://access.redhat.com/errata/RHSA-2026:21772)

## Related threats

- [undici HTTP client denial of service in decompress interceptor](https://junglewise.ai/threats/cve-2026-87029-undici-is-an-http-client-library-for-node-js-in-versions-7-15-0)
- [undici denial of service via TLS 1.2 certificate renegotiation](https://junglewise.ai/threats/cve-2026-87018-undici-is-an-http-client-library-for-node-js-in-versions-4-2-1)
- [undici WebSocket client denial of service via unbounded PONG buffering](https://junglewise.ai/threats/cve-2026-109932-undici-is-an-http-client-library-for-node-js-in-versions-5-15-0)
- [undici EventSource memory exhaustion denial of service](https://junglewise.ai/threats/cve-2026-109924-undici-is-an-http-client-library-for-node-js-in-versions-6-5-0)
- [undici HTTP client denial of service via excessive content-encodings](https://junglewise.ai/threats/cve-2026-109869-undici-is-an-http-client-library-for-node-js-in-versions-6-23-0)