CVE-2026-32689
Phoenix: Long-poll NDJSON body splitting causes large memory allocation
Description
### 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.
How to fix CVE-2026-32689
To remediate CVE-2026-32689, upgrade the affected package to a fixed version below.
- —upgrade to 1.7.22 or later
Is CVE-2026-32689 being exploited?
Low — EPSS is 0.5%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 1.7.0, < 1.7.22
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |