# CVE-2026-32689: Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix

> An attacker can crash the Phoenix server by sending a large NDJSON body to the long-poll transport, causing unbounded memory allocation.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 May 2026
- **Updated:** 7 May 2026
- **Also known as:** EEF-CVE-2026-32689, GHSA-628h-q48j-jr6q

## What is CVE-2026-32689?

CVE-2026-32689 is a high-severity denial of service vulnerability in phoenixframework phoenix, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-32689?

5 open source packages ship an affected version, including phoenix.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `phoenix` | Hex | From 1.7.0 | 1.7.22, 1.8.6 |
| `phoenix` | Hex | From 1.7.0 | 1.7.22 |
| `phoenix` | Hex | From 1.7.0 | 1.7.22 |
| `phoenix` | Hex | From 1.8.0 | 1.8.6 |
| `phoenix` | Hex | From 1.8.0 | 1.8.6 |

## How do I fix CVE-2026-32689?

Upgrade phoenix to a fixed version for your release line: 1.7.22 or 1.8.6.

## Is CVE-2026-32689 being exploited?

There is no known exploitation of CVE-2026-32689 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-32689 and fix it if it is affected.

What it is: CVE-2026-32689 is a high-severity denial of service vulnerability in phoenixframework phoenix, published on 5 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-32689 in the wild and no public exploit code.

Affected packages and fixed versions:
- phoenix (Hex): affected from 1.7.0; fixed in 1.7.22, 1.8.6
- phoenix (Hex): affected from 1.7.0; fixed in 1.7.22
- phoenix (Hex): affected from 1.7.0; fixed in 1.7.22
- phoenix (Hex): affected from 1.8.0; fixed in 1.8.6
- phoenix (Hex): affected from 1.8.0; fixed in 1.8.6

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-32689/ (Markdown: https://insights.sbomify.com/CVE-2026-32689/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32689
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32689
- OSV: https://osv.dev/vulnerability/CVE-2026-32689

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-32689/
Summaries are generated and may contain mistakes; the official description above is the record.