CVE-2026-116592

This vulnerability is rated as Important severity because successful exploitation can result in significant integrity and confidentiality compromises, allowing attackers to poison shared HTTP caches or expose private, user-specific responses. Risk is constrained to applications explicitly configured with an originless Agent combining shared response caching with automated redirect following. Workloads employing origin-bound dispatchers, isolated caching mechanisms, or redirection handling before caching are not susceptible to this flaw.

This flaw is a bypass of the incomplete fix for CVE-2026-109829 and is present only in undici 7.30.1 and 8.12.2-8.12.3; earlier 7.x/8.x versions fall within the scope of CVE-2026-109829, and fixed versions are 7.30.2 and 8.12.4. Node.js's built-in fetch API (which vendors undici internally) does not expose the vulnerable Agent/interceptor-composition configuration; exposure requires an application explicitly using the undici npm package with an originless Agent, a shared cache store, and compose(redirect(), cache()).

Configure Node.js applications utilizing undici to avoid vulnerable interceptor ordering:

1. Reorder interceptors: Structure the interceptor pipeline so caching is evaluated prior to redirection, such as using compose(cache(), redirect()).

2. Isolate cache boundaries: Replace shared originless Agent configurations with origin-bound Client or Pool dispatchers and separate cache stores.

3. Restrict shared caching: Disable shared caching on client requests that permit automated redirect following.

Caveats: Disabling shared caching or modifying dispatcher architecture may increase request latency and backend server load.

Warning: Applying these application configuration changes requires restarting the affected Node.js service.

--- CME Mitigation Guidance (2026-11-06) ---

Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to reconfigure undici interceptors to evaluate caching prior to redirection or isolate dispatchers and cache stores per origin: upgrade to undici 7.30.2, 8.12.4+ (or the corresponding fixed Red Hat builds), which account for intermediate redirect hops and enforce cache validation and header retention across all hops before storing responses under the original request key, closing all 3 injection vectors (intermediate redirect bounce through untrusted origin, dropping intermediate Vary header to expose private cached responses, laundering non-storable intermediate redirects via missing no-cache validation). Until patched, this is a concern on Node.js applications using an originless undici Agent composing redirect and shared cache interceptors, so reorder interceptors to evaluate cache before redirect, use origin-bound dispatchers with isolated cache stores, or disable shared caching on requests that permit redirect following. As a compensating measure, block outbound network connections to unapproved external endpoints to prevent reaching attacker-controlled intermediate redirect targets and restrict server-initiated requests and redirect hops to an explicit allowlist of permitted destinations. These controls limit blast radius and contain exploitation, but they do not fix the underlying intermediate redirect cache poisoning defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-208 Outbound Network Egress Restriction (SSRF Blast Radius Containment) (medium)