CVE-2026-32689 — phoenix
Fix: phoenixframework/phoenix@1a67c61CVE-2026-32689 is a CWE-770 vulnerability in phoenix. A fix is available for phoenix — see the affected versions and patch details below.
Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-32689.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
phoenix💧phoenixReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Hex packages — download data is not available via public APIs for these ecosystems.
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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💧Hex | phoenix | ≥ 1.7.0&&< 1.7.22 | 1.7.22mix deps.update phoenix |
| 💧Hex | phoenix | ≥ 1.8.0&&< 1.8.6 | 1.8.6mix deps.update phoenix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phoenix, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update phoenix to 1.7.22 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-32689 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-32689 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-32689. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-32689 in your dependencies?
O3 Security finds CVE-2026-32689 across Hex dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.