---
id: CVE-2026-16728
aliases:
  - GHSA-8xcm-r25x-g524
title: >-
  undici vulnerable to downstream response desynchronization via retry
  interceptor
summary: >-
  undici vulnerable to downstream response desynchronization via retry
  interceptor
severity: medium
cvss: 4.8
cwe:
  - CWE-444
vendor: undici
product: undici
ecosystem: npm
affected:
  - undici < 6.28.0
  - 'undici >= 7.0.0, < 7.29.0'
  - 'undici >= 8.0.0, < 8.9.0'
patched:
  - undici 6.28.0
  - undici 7.29.0
  - undici 8.9.0
published: '2026-08-03'
updated: '2026-08-03'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-8xcm-r25x-g524'
references:
  - url: 'https://github.com/nodejs/undici/security/advisories/GHSA-8xcm-r25x-g524'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-16728'
  - url: >-
      https://github.com/nodejs/undici/commit/1b5a5312c3a7d7a30c31bf0d000b39a8a2531e1c
  - url: >-
      https://github.com/nodejs/undici/commit/2b3f749336d356bbbc50192f87f6cf7bc714721a
  - url: >-
      https://github.com/nodejs/undici/commit/4a9dafb16ff43880cf590e6d9c2aeee25fbff6d7
  - url: >-
      https://github.com/nodejs/undici/commit/4fd5a0c61e627f928b7003adc4ffe1e55ec63420
  - url: >-
      https://github.com/nodejs/undici/commit/cba3a52ac2e7abcc4e656d82af8579ea82c2bb9e
  - url: >-
      https://github.com/nodejs/undici/commit/e11a68ed4ff345c79402476f7a00d473443e318d
  - url: 'https://hackerone.com/reports/3828685'
  - url: 'https://cna.openjsf.org/security-advisories.html'
  - url: 'https://github.com/nodejs/undici/releases/tag/v6.28.0'
  - url: 'https://github.com/nodejs/undici/releases/tag/v7.29.0'
  - url: 'https://github.com/nodejs/undici/releases/tag/v8.9.0'
  - url: 'https://github.com/advisories/GHSA-8xcm-r25x-g524'
tags:
  - ghsa
  - npm
epss: 0.00176
epssPercentile: 0.06346
ingestedAt: '2026-08-03T19:29:00.250Z'
---

## Overview

### Impact

Undici's `interceptors.retry()` can deliver a response whose body length does not match the `Content-Length` header exposed to the application after a retry or resume of a partial response. Applications that use `interceptors.retry()` and forward upstream response headers and bodies downstream, for example proxy or gateway applications, may emit an invalid HTTP response with a stale `Content-Length` header. This can lead to downstream response desynchronization, connection hangs, or response corruption in clients or intermediaries that rely on the forwarded framing metadata.

A malicious or faulty upstream can respond to a range request with a `206 Partial Content` response such as:

```http
Content-Range: bytes 0-99/300
Content-Length: 300
```

and then send only 99 bytes before closing the socket. `interceptors.retry()` can then retry with `Range: bytes=99-99`, receive the final byte, and deliver a 100-byte body to the application while the response headers still contain `Content-Length: 300` from the first response.

The bug requires `interceptors.retry()` to be enabled, an upstream that returns a partial response with a mismatched framing header, and a downstream forwarder that does not remove or recalculate `Content-Length`.

### Patches

Patched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.

### Workarounds

- Disable `interceptors.retry()` for untrusted upstreams.
- Remove or recalculate `Content-Length` before forwarding a response body assembled or transformed by Undici.

## Affected packages

- `undici < 6.28.0`
- `undici >= 7.0.0, < 7.29.0`
- `undici >= 8.0.0, < 8.9.0`

## Remediation

Upgrade to a patched release:

- `undici 6.28.0`
- `undici 7.29.0`
- `undici 8.9.0`