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.
History

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

{'score': 8.7, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: EEF

Published:

Updated: 2026-05-05T15:41:35.502Z

Reserved: 2026-03-13T09:12:14.475Z

Link: CVE-2026-32689

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-05-05T16:16:11.397

Modified: 2026-05-05T19:37:28.367

Link: CVE-2026-32689

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-05T18:30:29Z