next/image: /_next/image returns 500 (raw "fetch failed") when the remote host fails DNS or refuses the connection

Link to the code that reproduces this issue

https://github.com/matias-berger-atlas/next-image-enotfound-500-repro

To Reproduce

1. Clone the repro (next@16.3.4 pinned), npm install
2. next.config.ts allows does-not-resolve.example.invalid in images.remotePatterns; app/page.tsx renders one <Image> from that host
3. npm run build && npm start
4. curl -i 'http://localhost:3000/_next/image?url=https%3A%2F%2Fdoes-not-resolve.example.invalid%2Fa.jpg&w=640&q=75'

Current vs. Expected behavior

Current: 500 Internal Server Error, and the server logs

⨯ [TypeError: fetch failed]
  [cause]: Error: getaddrinfo ENOTFOUND does-not-resolve.example.invalid

Same for ECONNREFUSED and TLS handshake errors: any rejection of the upstream fetch().

Expected: a client-visible upstream error status (502 or 404) like every other upstream failure in the optimizer already produces. In fetchExternalImage:

const res = await fetch(href, { signal: AbortSignal.timeout(7000), redirect: 'manual' }).catch((err) => err)
if (res instanceof Error) {
  const err = res as Error
  if (err.name === 'TimeoutError') {
    throw new ImageError(504, '"url" parameter is valid but upstream response timed out')
  }
  throw err   // <-- raw TypeError('fetch failed') escapes; the route has no status for it => 500
}

Upstream timeout -> 504. Upstream non-2xx -> ImageError(res.status). Upstream too large -> 413. Only a rejected fetch (DNS failure, connection refused, TLS error) is rethrown raw and becomes a 500 with a stack trace in the logs. Still the case on 16.4.0-canary.26.

Why it matters: a third-party image CDN going dark (a real case for us: mediavault.point2.com stopped resolving, ~21k images) turns into a flood of 500s on the app's own ingress and alerts, for something that is entirely the upstream's fault and that the client <img onError> already handles fine when given a 4xx/5xx.

Suggested fix (we run this as a pnpm patch today):

throw new ImageError(502, '"url" parameter is valid but upstream request failed')

Provide environment information

Next.js 16.3.4 (also reproduced on 16.3.0 and 16.4.0-canary.26), Node 22, Linux (standalone, self-hosted), and locally on macOS.

Which area(s) are affected?

Image (next/image)

Which stage(s) are affected?

next start (local), Other (self-hosted / standalone)

Start with the linked reproduction, using next.config.ts, app/page.tsx, and the documented npm install, npm run build && npm start, and curl steps. Then inspect fetchExternalImage and its handling of rejected fetches. Done means DNS, connection-refused, and TLS failures return a client-visible upstream error such as 502 instead of an unhandled 500.