---
id: CVE-2026-9678
title: >-
  undici vulnerable to cross-user information disclosure via shared cache
  whitespace bypass
summary: >-
  undici vulnerable to cross-user information disclosure via shared cache
  whitespace bypass
severity: medium
cvss: 5.9
cwe:
  - CWE-524
vendor: undici
product: undici
affected:
  - 'undici >= 7.0.0, < 7.28.0'
  - 'undici >= 8.0.0, < 8.5.0'
patched:
  - undici 7.28.0
  - undici 8.5.0
published: '2026-06-18'
updated: '2026-06-18'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-pr7r-676h-xcf6'
references:
  - url: 'https://github.com/nodejs/undici/security/advisories/GHSA-pr7r-676h-xcf6'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-9678'
  - url: 'https://cna.openjsf.org/security-advisories.html'
  - url: 'https://github.com/advisories/GHSA-pr7r-676h-xcf6'
tags:
  - ghsa
  - npm
epss: 0.00388
epssPercentile: 0.32847
ingestedAt: '2026-06-19T03:39:00.823Z'
ecosystem: npm
---

## Overview

## Impact

Undici's cache interceptor incorrectly classifies some responses as cacheable when the upstream `Cache-Control` header uses whitespace-padded qualified `private` or `no-cache` field names such as `private=" authorization"` or `no-cache="\tauthorization"`. The parser preserves the surrounding whitespace, so later comparisons against the literal `authorization` field name fail and the response is stored.

In shared-cache mode, this allows a response containing one user's authenticated data to be served from cache to a subsequent caller, including an unauthenticated caller, when both requests resolve to the same cache key.

Affected applications are those that explicitly enable the cache interceptor (`interceptors.cache()`) in shared mode, forward `Authorization` headers upstream, and receive cacheable responses with non-canonical qualified `private` or `no-cache` directives.

## Patches

Upgrade to undici v7.28.0 or v8.5.0.

## Workarounds

If upgrade is not immediately possible, disable shared-cache mode for traffic that includes `Authorization` headers, avoid caching responses to authenticated requests, or add `Vary: Authorization` upstream.

## Affected packages

- `undici >= 7.0.0, < 7.28.0`
- `undici >= 8.0.0, < 8.5.0`

## Remediation

Upgrade to a patched release:

- `undici 7.28.0`
- `undici 8.5.0`