CVE-2026-109829: undici cache poisoning and cross-user disclosure via cross-origin redirects

CVE-2026-109829 · Severity: high · CVSS 7.4 · Published 2026-10-15

undici is an HTTP client library for Node.js used to make web requests from applications. When configured with specific interceptor settings and shared caching, an attacker controlling a redirect target can inject malicious responses into the cache that get served to legitimate users, or private user data can be exposed to unauthenticated callers. This can lead to data theft, account compromise, or serving of malicious content.

Technologies: undici (npm), OpenJS Foundation Undici. Vendors: npm, OpenJS Foundation.

Quick answers

Is CVE-2026-109829 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-109829 being exploited in the wild.
How severe is CVE-2026-109829?
High severity, with a CVSS score of 7.4, published 15 October 2026.
Which products and versions are affected?
undici (npm) >= 7.0.0, < 7.30.1, SEMVER:introduced=7.0.0,fixed=7.30.1; OpenJS Foundation Undici 7.0.0 through 7.30.0, 8.0.0 through 8.12.1.
Is there a fix for CVE-2026-109829?
Yes. undici (npm): upgrade to 7.30.1 or later. Until then: Compose the cache interceptor before the redirect interceptor as compose(cache(), redirect()), use per-origin dispatchers and cache stores instead of shared caches, or disable shared caching on redirect-capable requests. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-109829 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-109829?
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 7.30.1 or later
    npm install undici@7.30.1

Compose the cache interceptor before the redirect interceptor as compose(cache(), redirect()), use per-origin dispatchers and cache stores instead of shared caches, or disable shared caching on redirect-capable requests.

Technical details

The vulnerability occurs when an originless Agent composes redirect and cache interceptors in that specific order with a shared cache store; the cache key is built from the original request URL before the redirect handler changes the origin, causing cross-origin redirect responses to be cached under the original trusted URL's key. The cache_control policies of intermediate redirect hops are not preserved, allowing private or no-store responses to leak. Exploitation requires the specific composition of interceptors and shared cache in use; origin-bound dispatchers or reversed interceptor order are not affected.

Affected products

  • OpenJS Foundation undici 7.0.0 through 7.30.0, 8.0.0 through 8.12.1

Identifiers

  • CVE-2026-109829
  • GHSA-4w7w-5xrc-9h26

Timeline

  • 2026-10-15: disclosed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.