GHSA-628h-q48j-jr6q Phoenix: Long-poll NDJSON body splitting causes large memory allocation

• Hex phoenix: >= 1.7.0, < 1.7.22 → fixed in 1.7.22 • Hex phoenix: >= 1.8.0, < 1.8.6 → fixed in 1.8.6

Summary An unauthenticated denial-of-service vulnerability in Phoenix's long-poll transport allows a remote client to allocate a large amount of memory with a HTTP request. A handful of concurrent requests can be sufficient to let the node run out of memory. See also https://cna.erlef.org/cves/CVE-2026-32689.html. Details The unoptimised code path exists on the `application/x-ndjson` POST handling in the LongPoll transport. The endpoint requires only a session token, which any client can obtain by issuing a GET to the same URL with a matching `Origin` header, so exploitation is unauthenticated. Impact Anyone who runs a LiveView app with a public Longpoll socket or uses a `Phoenix.Socket` with longpoll option. Longpoll has been enabled for newly generated Phoenix projects since Phoenix 1.7.11.