In 'Elixir.Phoenix.Transports.LongPoll':publish/4, when a POST request is received with Content-Type: application/x-ndjson, the request body is split on newline characters using String.split/2 with no limit on the number of resulting segments. An attacker can send a body consisting entirely of newline bytes, causing a 1:1 amplification into a list of empty binaries — a 1 MB body produces approximately one million list elements, an 8 MB body approximately 8.4 million. Each element is then walked by Enum.map, materializing another list of the same size. This exhausts BEAM memory and schedulers, crashing the node and terminating all active sessions.
A session token required to reach the vulnerable endpoint is freely obtainable by any client via an unauthenticated GET request to the same URL with a matching Origin header, making this attack effectively unauthenticated.
This issue affects phoenix: from 1.7.0 before 1.7.22 and 1.8.6.
No advisories yet.
Solution
No solution given by the vendor.
Workaround
Disable the longpoll transport on all Phoenix.Socket declarations, including the LiveView /live socket, by removing or setting longpoll: false. Note that this prevents clients that cannot use WebSockets from connecting.
Tue, 05 May 2026 16:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix allows a denial of service via the long-poll transport's NDJSON body handling. In 'Elixir.Phoenix.Transports.LongPoll':publish/4, when a POST request is received with Content-Type: application/x-ndjson, the request body is split on newline characters using String.split/2 with no limit on the number of resulting segments. An attacker can send a body consisting entirely of newline bytes, causing a 1:1 amplification into a list of empty binaries — a 1 MB body produces approximately one million list elements, an 8 MB body approximately 8.4 million. Each element is then walked by Enum.map, materializing another list of the same size. This exhausts BEAM memory and schedulers, crashing the node and terminating all active sessions. A session token required to reach the vulnerable endpoint is freely obtainable by any client via an unauthenticated GET request to the same URL with a matching Origin header, making this attack effectively unauthenticated. This issue affects phoenix: from 1.7.0 before 1.7.22 and 1.8.6. | |
| Title | Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix | |
| First Time appeared |
Phoenixframework
Phoenixframework phoenix |
|
| Weaknesses | CWE-770 | |
| CPEs | cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Phoenixframework
Phoenixframework phoenix |
|
| References |
|
|
| Metrics |
cvssV4_0
|
Projects
Sign in to view the affected projects.
Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-05-05T15:41:35.502Z
Reserved: 2026-03-13T09:12:14.475Z
Link: CVE-2026-32689
No data.
Status : Deferred
Published: 2026-05-05T16:16:11.397
Modified: 2026-05-05T19:37:28.367
Link: CVE-2026-32689
No data.
OpenCVE Enrichment
Updated: 2026-05-05T18:30:29Z