CVE-2026-32689: Phoenix Long-poll NDJSON Body Splitting Causes Vulnerability

HIGH
Advisory Identifier: GHSA-628h-q48j-jr6q
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CWE-770
Published
Advisory Summary

CVE-2026-32689 is a HIGH long-poll ndjson body splitting causes vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Phoenix libraries in the Hex ecosystem. The issue involves long-poll ndjson body splitting causes large memory allocation. Remediation is available by upgrading affected packages to version 1.7.22, 1.8.6.

CVE-2026-32689 at a Glance

CVE Identifier CVE-2026-32689
GHSA Identifier GHSA-628h-q48j-jr6q
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Phoenix
Package Ecosystem Hex
Published Date
Last Updated

How to Fix CVE-2026-32689

To remediate this vulnerability, upgrade all affected Phoenix dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

phoenix fixed: 1.7.22 
Upgrade phoenix to 1.7.22
phoenix fixed: 1.8.6 
Upgrade phoenix to 1.8.6
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for phoenix

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-32689, inspect your project dependencies for Phoenix:

inspect dependencies for phoenix

Analyze the terminal output to locate any version of Phoenix in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.7.22), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Phoenix, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary An unauthenticated denial-of-service vulnerability in Phoenix's long-poll transport allows a remote client to allocate a large amount of memory with a HTTP request. A handful of concurrent requests can be sufficient to let the node run out of memory. See also https://cna.erlef.org/cves/CVE-2026-32689.html. ### Details The unoptimised code path exists on the `application/x-ndjson` POST handling in the LongPoll transport. The endpoint requires only a session token, which any client can obtain by issuing a GET to the same URL with a matching `Origin` header, so exploitation is unauthenticated. ### Impact Anyone who runs a LiveView app with a public Longpoll socket or uses a `Phoenix.Socket` with longpoll option. Longpoll has been enabled for newly generated Phoenix projects since Phoenix 1.7.11.

CVE-2026-32689 Affected Phoenix Versions

2 component(s)
Fixed Versions:
1.7.221.8.6
Product / Package Ecosystem Affected Versions Fixed Version
phoenix
 Hex
≥ 1.7.0
< 1.7.22
1.7.22
phoenix
 Hex
≥ 1.8.0
< 1.8.6
1.8.6

References

GitHub Advisory / Wiki ADVISORY
https://github.com/phoenixframework/phoenix/security/advisories/GHSA-628h-q48j-jr6q
NVD — CVE-2026-32689 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-32689
Security Fix Commit FIX COMMIT
https://github.com/phoenixframework/phoenix/commit/1a67c61ff9ce0a7711662ac7354861917a7c80f7
Security Fix Commit FIX COMMIT
https://github.com/phoenixframework/phoenix/commit/912ea181fd247c21dbcc49fb97d0053b947d81bf
cna.erlef.org/cves/cve-2026-32689... WEB
https://cna.erlef.org/cves/CVE-2026-32689.html
Phoenix Source Repository REPOSITORY
https://github.com/phoenixframework/phoenix
osv.dev/vulnerability/eef-c... WEB
https://osv.dev/vulnerability/EEF-CVE-2026-32689

Frequently Asked Questions

What is CVE-2026-32689?
CVE-2026-32689 is a security vulnerability in Phoenix involving Long-poll NDJSON body splitting causes large memory allocation under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Phoenix versions are affected?
Affected versions include releases prior to 1.7.22, 1.8.6 across affected packages: phoenix.
What version fixes CVE-2026-32689?
Upgrading to 1.7.22, 1.8.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is phoenix affected?
Yes, phoenix is affected in releases prior to 1.7.22, 1.8.6. Upgrade your dependency to 1.7.22, 1.8.6 or later.
What CWE is associated with CVE-2026-32689?
CVE-2026-32689 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check Hex dependencies for CVE-2026-32689?
Run the dependency tree command: 'inspect dependencies for phoenix'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-628h-q48j-jr6q",
  "modified" : "2026-05-08T20:24:15Z",
  "published" : "2026-05-08T20:24:15Z",
  "aliases" : [ "CVE-2026-32689" ],
  "summary" : "Phoenix: Long-poll NDJSON body splitting causes large memory allocation",
  "details" : "### Summary\n\nAn unauthenticated denial-of-service vulnerability in Phoenix's long-poll transport allows a remote client to allocate a large amount of memory with a HTTP request. A handful of concurrent requests can be sufficient to let the node run out of memory.\n\nSee also https://cna.erlef.org/cves/CVE-2026-32689.html.\n\n### Details\n\nThe unoptimised code path exists on the `application/x-ndjson` POST handling in the LongPoll transport. The endpoint requires only a session token, which any client can obtain by issuing a GET to the same URL with a matching `Origin` header, so exploitation is unauthenticated.\n\n### Impact\n\nAnyone who runs a LiveView app with a public Longpoll socket or uses a `Phoenix.Socket` with longpoll option.\nLongpoll has been enabled for newly generated Phoenix projects since Phoenix 1.7.11.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
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      "ecosystem" : "Hex",
      "name" : "phoenix"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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    } ]
  }, {
    "package" : {
      "ecosystem" : "Hex",
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    "ranges" : [ {
      "type" : "ECOSYSTEM",
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        "fixed" : "1.8.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-628h-q48j-jr6q"
  }, {
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  }, {
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    "url" : "https://github.com/phoenixframework/phoenix/commit/1a67c61ff9ce0a7711662ac7354861917a7c80f7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/phoenixframework/phoenix/commit/912ea181fd247c21dbcc49fb97d0053b947d81bf"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-32689.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/phoenixframework/phoenix"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-32689"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T20:24:15Z",
    "nvd_published_at" : "2026-05-05T16:16:11Z"
  }
}