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CVE-2026-59248

Full vulnerability record from the local CVENow database.

Description

Allocation of resources without limits vulnerability in ninenines cowlib allows an unauthenticated remote HTTP/2 or HTTP/3 peer to exhaust memory on the vulnerable server (or client) and cause a denial of service. The HPACK and QPACK prefixed-integer decoder cow_hpack_common:dec_big_int/3 in src/cow_hpack_common.hrl (invoked from cow_hpack:decode/2 in src/cow_hpack.erl and from cow_qpack:decode_field_section/3 in src/cow_qpack.erl) reads continuation octets until it sees one whose high bit is clear, evaluating Int + (Value bsl M) at each step with the shift M growing by seven per octet. No limit is enforced on the number of continuation octets, on the resulting bit width, or on the value; the decoder consumes whatever encoded length the peer supplies. Because Erlang integers are immutable, each intermediate Value bsl M and each accumulator update allocates a fresh bignum whose digit width grows linearly with the number of octets processed so far. Summed across the whole decode, the transient bignum digit materialization is on the order of the square of the encoded length. A single maximal HPACK indexed representation carried inside one HTTP/2 HEADERS plus one CONTINUATION frame at Cowboy's default max_frame_size_received can force hundreds of megabytes of transient allocation and garbage-collection churn before the resulting header-table index is rejected as invalid. Repeated or concurrent connections multiply the pressure and can drive the Erlang VM to memory exhaustion. Cowlib is the HTTP parser used by Cowboy, RabbitMQ's management plugin, and other Erlang and Elixir HTTP/2 and HTTP/3 servers and clients, so any exposed endpoint that accepts HPACK or QPACK from an untrusted peer is reachable. This issue affects cowlib: from 2.0.0 before 2.19.0.

Severity
HIGH
CVSS score
8.7 (v4.0)
Vulnerability status
Deferred
Source identifier
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Published
2026-07-28 10:16:50.083000
Last modified
2026-10-24 13:10:00.147000
View original CVE JSON 
{
  "id": "CVE-2026-59248",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "published": "2026-07-28T10:16:50.083",
  "lastModified": "2026-10-24T13:10:00.147",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Allocation of resources without limits vulnerability in ninenines cowlib allows an unauthenticated remote HTTP/2 or HTTP/3 peer to exhaust memory on the vulnerable server (or client) and cause a denial of service.\n\nThe HPACK and QPACK prefixed-integer decoder cow_hpack_common:dec_big_int/3 in src/cow_hpack_common.hrl (invoked from cow_hpack:decode/2 in src/cow_hpack.erl and from cow_qpack:decode_field_section/3 in src/cow_qpack.erl) reads continuation octets until it sees one whose high bit is clear, evaluating Int + (Value bsl M) at each step with the shift M growing by seven per octet. No limit is enforced on the number of continuation octets, on the resulting bit width, or on the value; the decoder consumes whatever encoded length the peer supplies.\n\nBecause Erlang integers are immutable, each intermediate Value bsl M and each accumulator update allocates a fresh bignum whose digit width grows linearly with the number of octets processed so far. Summed across the whole decode, the transient bignum digit materialization is on the order of the square of the encoded length. A single maximal HPACK indexed representation carried inside one HTTP/2 HEADERS plus one CONTINUATION frame at Cowboy's default max_frame_size_received can force hundreds of megabytes of transient allocation and garbage-collection churn before the resulting header-table index is rejected as invalid. Repeated or concurrent connections multiply the pressure and can drive the Erlang VM to memory exhaustion.\n\nCowlib is the HTTP parser used by Cowboy, RabbitMQ's management plugin, and other Erlang and Elixir HTTP/2 and HTTP/3 servers and clients, so any exposed endpoint that accepts HPACK or QPACK from an untrusted peer is reachable.\n\nThis issue affects cowlib: from 2.0.0 before 2.19.0."
    },
    {
      "lang": "es",
      "value": "La vulnerabilidad de asignación de recursos sin límites en ninenines cowlib permite que un par HTTP/2 o HTTP/3 remoto no autenticado agote la memoria en el servidor (o cliente) vulnerable y cause una denegación de servicio.\n\nEl decodificador de enteros con prefijo HPACK y QPACK cow_hpack_common:dec_big_int/3 en src/cow_hpack_common.hrl (invocado desde cow_hpack:decode/2 en src/cow_hpack.erl y desde cow_qpack:decode_field_section/3 en src/cow_qpack.erl) lee octetos de continuación hasta que ve uno cuyo bit más significativo está claro, evaluando Int + (Value bsl M) en cada paso con el desplazamiento M creciendo en siete por octeto. No se impone ningún límite en el número de octetos de continuación, en el ancho de bits resultante o en el valor; el decodificador consume cualquier longitud codificada que el par suministre.\n\nDebido a que los enteros de Erlang son inmutables, cada Value bsl M intermedio y cada actualización del acumulador asigna un nuevo bignum cuyo ancho de dígito crece linealmente con el número de octetos procesados hasta ahora. Sumado a lo largo de toda la decodificación, la materialización transitoria de dígitos bignum es del orden del cuadrado de la longitud codificada. Una única representación indexada HPACK máxima transportada dentro de un frame HTTP/2 HEADERS más un frame CONTINUATION en el max_frame_size_received predeterminado de Cowboy puede forzar cientos de megabytes de asignación transitoria y agitación de recolección de basura antes de que el índice de la tabla de encabezados resultante sea rechazado como inválido. Las conexiones repetidas o concurrentes multiplican la presión y pueden llevar a la VM de Erlang al agotamiento de la memoria.\n\nCowlib es el analizador HTTP utilizado por Cowboy, el plugin de gestión de RabbitMQ, y otros servidores y clientes HTTP/2 y HTTP/3 de Erlang y Elixir, por lo que cualquier punto final expuesto que acepte HPACK o QPACK de un par no confiable es alcanzable.\n\nEste problema afecta a cowlib: desde 2.0.0 antes de 2.19.0."
    }
  ],
  "affected": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "affectedData": [
        {
          "vendor": "ninenines",
          "product": "cowlib",
          "defaultStatus": "unaffected",
          "collectionURL": "https://repo.hex.pm",
          "packageName": "cowlib",
          "cpes": [
            "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "cow_hpack",
            "cow_qpack"
          ],
          "programFiles": [
            "src/cow_hpack_common.hrl",
            "src/cow_hpack.erl",
            "src/cow_qpack.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_hpack:decode/2"
            },
            {
              "name": "cow_qpack:decode_field_section/3"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:hex/cowlib",
          "versions": [
            {
              "version": "2.0.0-pre.1",
              "lessThan": "2.19.0",
              "versionType": "semver",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "ninenines",
          "product": "cowlib",
          "defaultStatus": "unaffected",
          "collectionURL": "https://github.com",
          "packageName": "ninenines/cowlib",
          "cpes": [
            "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"
          ],
          "modules": [
            "cow_hpack",
            "cow_qpack"
          ],
          "programFiles": [
            "src/cow_hpack_common.hrl",
            "src/cow_hpack.erl",
            "src/cow_qpack.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_hpack:decode/2"
            },
            {
              "name": "cow_qpack:decode_field_section/3"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:github/ninenines/cowlib",
          "versions": [
            {
              "version": "5ddecbc121f812aec53d9df91829448d8e94e44c",
              "lessThan": "f582430498072a0c65ad338030321576dc13a343",
              "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: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",
          "baseScore": 8.7,
          "baseSeverity": "HIGH",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnAvailabilityImpact": "HIGH",
          "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": "2026-07-28T12:39:48.662716Z",
          "id": "CVE-2026-59248",
          "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-2026-59248.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://github.com/ninenines/cowlib/commit/f582430498072a0c65ad338030321576dc13a343",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    },
    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-59248",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ]
}