Vulnerability · Published May 5, 2026 · Assigned by EEF
CVE-2026-32689Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix
High 8.7
In plain English
A high-severity resource allocation without limits in phoenix from phoenixframework. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).
Official 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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| phoenixframework | phoenix | 1.7.0 – before 1.7.221.8.0 – before 1.8.6 |
| phoenixframework | phoenix | 2674c6ea30634667f9b09966b90269393b445953 – before * |
Weakness: CWE-770 · 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
References
- https://github.com/phoenixframework/phoenix/security/advisories/GHSA-628h-q48j-jr6q vendor-advisory, related
- https://cna.erlef.org/cves/CVE-2026-32689.html related
- https://osv.dev/vulnerability/EEF-CVE-2026-32689 related
- https://github.com/phoenixframework/phoenix/commit/1a67c61ff9ce0a7711662ac7354861917a7c80f7 patch
- https://github.com/phoenixframework/phoenix/commit/912ea181fd247c21dbcc49fb97d0053b947d81bf patch