---
id: "CVE-2026-119348"
page: "https://infrastack.ai/live/CVE-2026-119348"
kind: "vulnerability"
aliases: ["CVE-2026-119348", "GHSA-pc58-hwjq-p385"]
title: "Cross-client response injection and disclosure in self-hosted Next.js applications forwarding fetched responses"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "next", "fixed": ["16.4.5"], "affected": ">= 16.0.0, <= 16.4.4", "ecosystem": "npm"}, {"name": "next", "fixed": ["15.5.29"], "affected": "<= 15.5.28", "ecosystem": "npm"}]
ecosystems: ["npm"]
tags: ["next.js", "npm", "runtime", "self-hosted"]
not_affected_if: ["managed-hosting", "no-upstream-passthrough"]
published_at: "2026-11-03T18:39:48+00:00"
first_seen_at: "2026-11-09T22:53:14+00:00"
updated_at: "2026-11-09T22:54:48+00:00"
sources: [{"source": "ghsa-repo", "url": "https://github.com/vercel/next.js/security/advisories/GHSA-pc58-hwjq-p385", "first_seen_at": "2026-11-09T22:53:14+00:00"}]
exploit_sources: []
---

# Cross-client response injection and disclosure in self-hosted Next.js applications forwarding fetched responses

Link for people: https://infrastack.ai/live/CVE-2026-119348 (this .md is for agents)

Self-hosted Next.js apps that pass a fetched upstream response through unchanged can send a response whose framing does not match its body. Behind an HTTP/1.1 reverse proxy that allows pipelined responses, an attacker can desynchronize responses and read or inject another client's responses.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- npm:next affected >= 16.0.0, <= 16.4.4 fixed 16.4.5
- npm:next affected <= 15.5.28 fixed 15.5.29

## How to check

- Check the installed version with `npm ls next` and compare it to the fixed versions.
- Look for App Router route handlers or fetch-cache code that returns a `fetch()` response object unchanged.
- Check whether the app sits behind an HTTP/1.1 reverse proxy that permits pipelined response queueing.

## Fix

- `next` 16.x: move to `16.4.5`
- `next` 15.x: move to `15.5.29`

## Timeline

- 2026-11-09T22:53:14+00:00 ghsa-repo https://github.com/vercel/next.js/security/advisories/GHSA-pc58-hwjq-p385

## Documents

- [advisory] Maintainer's advisory: github.com https://github.com/vercel/next.js/security/advisories/GHSA-pc58-hwjq-p385

## From the sources

<!-- https://linear.app/vercel/issue/NSEC-564 -->
Self-hosted Next.js applications (App Router route handlers and the fetch cache) that return a fetched upstream response unchanged can emit a response whose declared framing does not match the body actually sent. When such an application sits behind an HTTP/1.1 reverse proxy that permits pipelined response queueing, a crafted upstream response can desynchronize responses between clients, enabling response injection and disclosure of other clients' responses.

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