FKIE_CVE-2026-56811

Vulnerability from fkie_nvd - Published: 2026-07-07 16:16 - Updated: 2026-07-09 14:59
Severity
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll). This vulnerability is associated with program files lib/phoenix/socket.ex and program routine 'Elixir.Phoenix.Socket':handle_in/4. Phoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it. The fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them. This issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9.
References
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://cna.erlef.org/cves/CVE-2026-56811.htmlPatch, Third Party Advisory, Mitigation
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/phoenixframework/phoenix/commit/16e295d2fccab185d1292322e2bee5d46c725c8aPatch
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/phoenixframework/phoenix/commit/a612100cd8a4279091abc1a2ef8fb98a6d01c0a1Patch
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/phoenixframework/phoenix/commit/c498ba8cf49f6accbbd0c643a5340b58db891218Patch
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/phoenixframework/phoenix/commit/d19ca0a8d9f82c130b7ed339b9f033433e2dea5ePatch
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485wPatch, Vendor Advisory
6b3ad84c-e1a6-4bf7-a703-f496b71e49dbhttps://osv.dev/vulnerability/EEF-CVE-2026-56811Third Party Advisory, Mitigation
Impacted products
Vendor Product Version
phoenixframework phoenix *
phoenixframework phoenix *
phoenixframework phoenix *
phoenixframework phoenix *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Phoenix.Socket\u0027"
          ],
          "packageName": "phoenix",
          "packageURL": "pkg:hex/phoenix",
          "product": "phoenix",
          "programFiles": [
            "lib/phoenix/socket.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
            }
          ],
          "repo": "https://github.com/phoenixframework/phoenix",
          "vendor": "phoenixframework",
          "versions": [
            {
              "lessThan": "1.5.15",
              "status": "affected",
              "version": "0.11.0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.6.17",
              "status": "affected",
              "version": "1.6.0-rc.0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.7.24",
              "status": "affected",
              "version": "1.7.0-rc.0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.8.9",
              "status": "affected",
              "version": "1.8.0-rc.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.Phoenix.Socket\u0027"
          ],
          "packageName": "phoenixframework/phoenix",
          "packageURL": "pkg:github/phoenixframework/phoenix",
          "product": "phoenix",
          "programFiles": [
            "lib/phoenix/socket.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.Phoenix.Socket\u0027:handle_in/4"
            }
          ],
          "repo": "https://github.com/phoenixframework/phoenix",
          "vendor": "phoenixframework",
          "versions": [
            {
              "changes": [
                {
                  "at": "c498ba8cf49f6accbbd0c643a5340b58db891218",
                  "status": "unaffected"
                },
                {
                  "at": "d19ca0a8d9f82c130b7ed339b9f033433e2dea5e",
                  "status": "unaffected"
                },
                {
                  "at": "a612100cd8a4279091abc1a2ef8fb98a6d01c0a1",
                  "status": "unaffected"
                },
                {
                  "at": "16e295d2fccab185d1292322e2bee5d46c725c8a",
                  "status": "unaffected"
                }
              ],
              "lessThan": "*",
              "status": "affected",
              "version": "14a297e88023cb280a577962a49a0bbdeef9f4eb",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "3CF8EA55-C063-4742-87ED-53E1998977B5",
              "versionEndExcluding": "1.5.15",
              "versionStartIncluding": "1.2.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "809E49A8-D727-4E05-BBF9-F9E34077E4A4",
              "versionEndExcluding": "1.6.17",
              "versionStartIncluding": "1.6.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "3257C901-8FC3-4107-95C6-C57F909FFE40",
              "versionEndExcluding": "1.7.24",
              "versionStartIncluding": "1.7.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:phoenixframework:phoenix:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "8F98C1AC-1593-43EB-929A-4D3B7597C9BC",
              "versionEndExcluding": "1.8.9",
              "versionStartIncluding": "1.8.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix (Phoenix.Socket module) allows an unauthenticated attacker to cause a denial of service against any endpoint that mounts a Phoenix socket with a reachable channel transport (WebSocket or LongPoll).\n\nThis vulnerability is associated with program files lib/phoenix/socket.ex and program routine \u0027Elixir.Phoenix.Socket\u0027:handle_in/4.\n\nPhoenix transports do not limit the number of channels that a single transport process may join. Every phx_join message a client sends over one connection starts a persistent channel process, and the socket process accepts an unbounded number of them. A single unauthenticated client can therefore open one WebSocket or LongPoll connection and stream a large number of phx_join messages, spawning hundreds of thousands of channel processes over that one connection and eventually reaching the BEAM maximum process limit. Once the process table is exhausted the virtual machine can no longer start new processes, denying service to legitimate traffic across the whole node. Because the amplification happens inside a single connection, network-layer connection caps and rate limiting do not mitigate it.\n\nThe fix adds a :max_channels_per_transport option (default 100) that bounds the number of channels a single transport process can join, forcing abusive clients to open many connections instead, where external load balancers and reverse proxies can throttle them.\n\nThis issue affects phoenix: from 0.11.0 before 1.5.15, from 1.6.0-rc.0 before 1.6.17, from 1.7.0-rc.0 before 1.7.24, and from 1.8.0-rc.0 before 1.8.9."
    }
  ],
  "id": "CVE-2026-56811",
  "lastModified": "2026-07-09T14:59:45.367",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.7,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "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",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-56811",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-07T16:12:27.662417Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-07T16:16:40.710",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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        "Third Party Advisory",
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      ],
      "url": "https://cna.erlef.org/cves/CVE-2026-56811.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
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    },
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      "tags": [
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      "url": "https://github.com/phoenixframework/phoenix/security/advisories/GHSA-6983-jfq8-485w"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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        "Mitigation"
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      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-56811"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}



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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

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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.


Detection rules are retrieved from Rulezet.