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Fencer Vulns
high 8.7

CVE-2026-32689 json

Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix

published 2026-05-05 6 mo ago modified 2026-10-26 13 d ago also EEF-CVE-2026-32689 , EUVD-2026-27339 , GHSA-628h-q48j-jr6q

cvss
8.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

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.

Patch / fix

  • hex phoenix 1.7.22, 1.8.6
  • phoenixframework phoenix 1.7.22, 1.8.6

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 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
CNA 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
hex phoenix
>=1.7.0, <1.7.22
>=1.8.0, <1.8.6
1.7.22
1.8.6

Affected products

  • phoenixframework phoenix

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.