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CVE-2026-65624

Full vulnerability record from the local CVENow database.

Description

Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP/1.1. The HTTP/1.1 handler in cowboy_http enforces the max_headers limit by counting the number of distinct header names in a map (maps:size(Headers)). When a request contains multiple header lines with the same name, the values are concatenated into a single ever-growing binary stored under that one map key (", " for regular headers, "; " for cookies), so the map size stays at one and the max_headers cap (default 100) is never reached. Because no accumulator bounds the total number of header lines or the total byte size of the header block (only per-line max_header_name_length and max_header_value_length apply), an unauthenticated client can send an arbitrary number of header lines with the same name and grow the connection process's binary memory to arbitrary size within the request window. The impact per connection is bounded by request_timeout (default 5 seconds, not reset by header data), and by max_heap_size when set (the offending connection process is killed once its heap grows past the limit). When max_heap_size is left at the default (unset), sustained abuse can drive the Erlang VM into out-of-memory conditions. This issue affects cowboy from 2.0.0-pre.4 before 2.18.0.

Severity
MEDIUM
CVSS score
6.9 (v4.0)
Vulnerability status
Deferred
Source identifier
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Published
2026-07-28 10:16:50.500000
Last modified
2026-10-24 13:10:00.147000
View original CVE JSON 
{
  "id": "CVE-2026-65624",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "published": "2026-07-28T10:16:50.500",
  "lastModified": "2026-10-24T13:10:00.147",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP/1.1.\n\nThe HTTP/1.1 handler in cowboy_http enforces the max_headers limit by counting the number of distinct header names in a map (maps:size(Headers)). When a request contains multiple header lines with the same name, the values are concatenated into a single ever-growing binary stored under that one map key (\", \" for regular headers, \"; \" for cookies), so the map size stays at one and the max_headers cap (default 100) is never reached. Because no accumulator bounds the total number of header lines or the total byte size of the header block (only per-line max_header_name_length and max_header_value_length apply), an unauthenticated client can send an arbitrary number of header lines with the same name and grow the connection process's binary memory to arbitrary size within the request window.\n\nThe impact per connection is bounded by request_timeout (default 5 seconds, not reset by header data), and by max_heap_size when set (the offending connection process is killed once its heap grows past the limit). When max_heap_size is left at the default (unset), sustained abuse can drive the Erlang VM into out-of-memory conditions.\n\nThis issue affects cowboy from 2.0.0-pre.4 before 2.18.0."
    },
    {
      "lang": "es",
      "value": "Vulnerabilidad de asignación de recursos sin límites ni limitación en ninenines cowboy permite a un atacante remoto no autenticado agotar la memoria del proceso de conexión a través de HTTP/1.1.\n\nEl gestor HTTP/1.1 en cowboy_http aplica el límite max_headers contando el número de nombres de encabezado distintos en un mapa (maps:size(Headers)). Cuando una solicitud contiene múltiples líneas de encabezado con el mismo nombre, los valores se concatenan en un único binario en constante crecimiento almacenado bajo esa única clave de mapa (’, ’ para encabezados regulares, ’; ’ para cookies), por lo que el tamaño del mapa permanece en uno y el límite max_headers (predeterminado 100) nunca se alcanza. Debido a que ningún acumulador limita el número total de líneas de encabezado o el tamaño total en bytes del bloque de encabezado (solo se aplican max_header_name_length y max_header_value_length por línea), un cliente no autenticado puede enviar un número arbitrario de líneas de encabezado con el mismo nombre y aumentar la memoria binaria del proceso de conexión a un tamaño arbitrario dentro de la ventana de solicitud.\n\nEl impacto por conexión está limitado por request_timeout (predeterminado 5 segundos, no se restablece por los datos del encabezado), y por max_heap_size cuando se establece (el proceso de conexión infractor se termina una vez que su heap supera el límite). Cuando max_heap_size se deja en el valor predeterminado (no establecido), el abuso sostenido puede llevar a la VM de Erlang a condiciones de falta de memoria.\n\nEste problema afecta a cowboy desde 2.0.0-pre.4 antes de 2.18.0."
    }
  ],
  "affected": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "affectedData": [
        {
          "vendor": "ninenines",
          "product": "cowboy",
          "defaultStatus": "unaffected",
          "collectionURL": "https://repo.hex.pm",
          "packageName": "cowboy",
          "cpes": [
            "cpe:2.3:a:ninenines:cowboy:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "cowboy_http"
          ],
          "programFiles": [
            "src/cowboy_http.erl"
          ],
          "programRoutines": [
            {
              "name": "cowboy_http:parse_header/3"
            },
            {
              "name": "cowboy_http:parse_hd_value/6"
            }
          ],
          "repo": "https://github.com/ninenines/cowboy",
          "packageURL": "pkg:hex/cowboy",
          "versions": [
            {
              "version": "2.0.0-pre.4",
              "lessThan": "2.18.0",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "ninenines",
          "product": "cowboy",
          "defaultStatus": "unaffected",
          "collectionURL": "https://github.com",
          "packageName": "ninenines/cowboy",
          "cpes": [
            "cpe:2.3:a:ninenines:cowboy:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "cowboy_http"
          ],
          "programFiles": [
            "src/cowboy_http.erl"
          ],
          "programRoutines": [
            {
              "name": "cowboy_http:parse_header/3"
            },
            {
              "name": "cowboy_http:parse_hd_value/6"
            }
          ],
          "repo": "https://github.com/ninenines/cowboy",
          "packageURL": "pkg:github/ninenines/cowboy",
          "versions": [
            {
              "version": "309780a9fda145c262a47ac7811ffd50a0271c5b",
              "lessThan": "3a34d8c1cfd94326466aa16a9017236691dc9c55",
              "versionType": "git",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
      {
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary",
        "cvssData": {
          "version": "4.0",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnAvailabilityImpact": "LOW",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "subAvailabilityImpact": "NONE",
          "exploitMaturity": "NOT_DEFINED",
          "confidentialityRequirement": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "valueDensity": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED"
        }
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-28T12:38:53.899266Z",
          "id": "CVE-2026-65624",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-65624.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ninenines/cowboy/commit/3a34d8c1cfd94326466aa16a9017236691dc9c55",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-65624",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ]
}