GHSA-6983-JFQ8-485W

Vulnerability from github – Published: 2026-09-03 20:33 – Updated: 2026-09-03 20:33
VLAI
Summary
Phoenix: Unbounded channel joins per transport enables DoS over few connections
Details

Summary

Phoenix transports do not limit the number of channels in a given connection, making it easy to spawn hundreds of thousands of processes over a single connection, and, eventually reaching the max processes VM limit. The solution is to limit the number of channels per transport, so an attacker needs to start new HTTP/WebSocket connections, allowing third-party services to apply rate limits and intervene more easily.

Impact

An unauthenticated remote attacker can cause a denial of service against any Phoenix app that exposes LongPoll/WebSocket transports.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Hex",
        "name": "phoenix"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.11.0"
            },
            {
              "fixed": "1.5.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Hex",
        "name": "phoenix"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.6.0-rc.0"
            },
            {
              "fixed": "1.6.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Hex",
        "name": "phoenix"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.7.0-rc.0"
            },
            {
              "fixed": "1.7.24"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Hex",
        "name": "phoenix"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.8.0-rc.0"
            },
            {
              "fixed": "1.8.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-56811"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-03T20:33:03Z",
    "nvd_published_at": "2026-07-07T16:16:40Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nPhoenix transports do not limit the number of channels in a given connection, making it easy to spawn hundreds of thousands of processes over a single connection, and, eventually reaching the max processes VM limit. The solution is to limit the number of channels per transport, so an attacker needs to start new HTTP/WebSocket connections, allowing third-party services to apply rate limits and intervene more easily.\n\n### Impact\n\nAn unauthenticated remote attacker can cause a denial of service against any Phoenix app that exposes LongPoll/WebSocket transports.",
  "id": "GHSA-6983-jfq8-485w",
  "modified": "2026-09-03T20:33:03Z",
  "published": "2026-09-03T20:33:03Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56811"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8a"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218"
    },
    {
      "type": "WEB",
      "url": "https://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5e"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-56811.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/phoenixframework/phoenix"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Phoenix: Unbounded channel joins per transport enables DoS over few connections"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.