# CVE-2026-109869: undici HTTP client denial of service via excessive content-encodings

Source: https://junglewise.ai/threats/cve-2026-109869-undici-is-an-http-client-library-for-node-js-in-versions-6-23-0  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-15. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-109869 · Severity: high · CVSS 7.5 · Published 2026-10-15

undici is an HTTP client library for Node.js that applications use to make web requests. A remote server can crash the entire Node.js process by sending a specially crafted response with excessive content-encoding headers and then closing the connection early, causing a denial of service even if the application handles the error correctly.

Technologies: [undici (npm)](https://junglewise.ai/threats/technologies/undici), [OpenJS Foundation Undici](https://junglewise.ai/threats/technologies/openjs-foundation-undici). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [OpenJS Foundation](https://junglewise.ai/threats/vendors/openjs-foundation).

## Quick answers

**Is CVE-2026-109869 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109869 being exploited in the wild.

**How severe is CVE-2026-109869?** High severity, with a CVSS score of 7.5, published 15 October 2026.

**Which products and versions are affected?** undici (npm) >= 6.23.0, < 6.29.1, SEMVER:introduced=6.23.0,fixed=6.29.1; OpenJS Foundation Undici 6.23.0 through 6.29.0, 7.18.0 through 7.30.0, 8.0.0 through 8.12.1.

**Is there a fix for CVE-2026-109869?** Yes. undici (npm): upgrade to 6.29.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-109869 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-109869?** Check whether you run undici (npm) or OpenJS Foundation Undici 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 6.29.1 or later

  ```sh
  npm install undici@6.29.1
  ```


## Technical details

The fetch() implementation creates an internal response stream before validating the content-encoding chain against its limit of five codings. When a server returns more than five encodings and closes the connection before sending the body, undici rejects the request but leaves the stream orphaned without error handling, causing Node.js to treat the resulting content-length mismatch as an unhandled error and terminate the process. This requires only network access and a single response from a malicious server; no authentication or user interaction is needed.

## Affected products

- OpenJS Foundation undici 6.23.0 through 6.29.0, 7.18.0 through 7.30.0, 8.0.0 through 8.12.1

## Identifiers

- CVE-2026-109869
- GHSA-xjj6-f33q-929c

## Timeline

- 2026-10-15: disclosed
- 2026-10-15: patched

## References

- [https://cna.openjsf.org/security-advisories.html](https://cna.openjsf.org/security-advisories.html)
- [https://github.com/nodejs/undici/security/advisories/GHSA-xjj6-f33q-929c](https://github.com/nodejs/undici/security/advisories/GHSA-xjj6-f33q-929c)

## Related threats

- [undici cross-user cache disclosure via same-origin redirect](https://junglewise.ai/threats/cve-2026-120474-undici-is-an-http-client-for-node-js-in-versions-7-0-0-through-7)
- [undici Subresource Integrity bypass via whitespace in integrity metadata](https://junglewise.ai/threats/cve-2026-120423-undici-is-an-http-client-for-node-js-in-versions-7-15-0-through)
- [undici denial of service via unhandled exception in cache-interceptor](https://junglewise.ai/threats/cve-2026-120222-undici-is-an-http-client-for-node-js-in-versions-7-0-0-through-7)
- [undici cache poisoning and cross-user disclosure via intermediate redirect](https://junglewise.ai/threats/cve-2026-116592-undici-is-an-http-client-for-node-js-in-versions-7-30-1-and-8-12)
- [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)