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CVE-2026-7790

Full vulnerability record from the local CVENow database.

Description

Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation. The chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on each partial read and restarts from zero on resumption, raising the cost to O(N³). An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request with Transfer-Encoding: chunked and a very long chunk-size hex string to cause denial of service through CPU exhaustion and memory amplification. This vulnerability is associated with program file src/cow_http_te.erl and program routines cow_http_te:stream_chunked/2, cow_http_te:chunked_len/4. This issue affects cowlib: from 0.6.0 before 2.16.1.

Severity
HIGH
CVSS score
8.7 (v4.0)
Vulnerability status
Analyzed
Source identifier
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Published
2026-05-11 19:16:29.477000
Last modified
2026-10-26 18:10:00.173000
View original CVE JSON 
{
  "id": "CVE-2026-7790",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "published": "2026-05-11T19:16:29.477",
  "lastModified": "2026-10-26T18:10:00.173",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Uncontrolled Resource Consumption vulnerability in ninenines cowlib (cow_http_te module) allows Excessive Allocation.\n\nThe chunked transfer-encoding parser in cow_http_te accepts an unbounded number of hex digits in the chunk-size field. Each digit causes a bignum multiplication (Len * 16 + digit), so parsing N hex digits requires O(N²) CPU work and O(N) memory. Additionally, when input is drip-fed, the parser discards the accumulated length on each partial read and restarts from zero on resumption, raising the cost to O(N³). An unauthenticated remote attacker can exploit this by sending an HTTP/1.1 request with Transfer-Encoding: chunked and a very long chunk-size hex string to cause denial of service through CPU exhaustion and memory amplification.\n\nThis vulnerability is associated with program file src/cow_http_te.erl and program routines cow_http_te:stream_chunked/2, cow_http_te:chunked_len/4.\n\nThis issue affects cowlib: from 0.6.0 before 2.16.1."
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad de consumo de recursos no controlado en ninenines cowlib (módulo cow_http_te) permite una asignación excesiva.\n\nEl analizador de codificación de transferencia por bloques en cow_http_te acepta un número ilimitado de dígitos hexadecimales en el campo de tamaño de bloque (’chunk-size’). Cada dígito provoca una multiplicación de número grande (’bignum’) (Len * 16 + dígito), por lo que analizar N dígitos hexadecimales requiere un trabajo de CPU de O(N²) y una memoria de O(N). Además, cuando la entrada se alimenta por goteo, el analizador descarta la longitud acumulada en cada lectura parcial y se reinicia desde cero al reanudarse, elevando el costo a O(N³). Un atacante remoto no autenticado puede explotar esto enviando una solicitud HTTP/1.1 con Transfer-Encoding: chunked y una cadena hexadecimal de tamaño de bloque (’chunk-size’) muy larga para causar denegación de servicio a través del agotamiento de la CPU y la amplificación de la memoria.\n\nEsta vulnerabilidad está asociada con el archivo de programa src/cow_http_te.erl y las rutinas de programa cow_http_te:stream_chunked/2, cow_http_te:chunked_len/4.\n\nEste problema afecta a cowlib: desde 0.6.0 antes de 2.16.1."
    }
  ],
  "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_http_te"
          ],
          "programFiles": [
            "src/cow_http_te.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_http_te:stream_chunked/2"
            },
            {
              "name": "cow_http_te:chunked_len/4"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:hex/cowlib",
          "versions": [
            {
              "version": "0.6.0",
              "lessThan": "2.16.1",
              "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_http_te"
          ],
          "programFiles": [
            "src/cow_http_te.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_http_te:stream_chunked/2"
            },
            {
              "name": "cow_http_te:chunked_len/4"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:github/ninenines/cowlib",
          "versions": [
            {
              "version": "8c0e428b012c59f553a264f285ed89d36f791e3e",
              "lessThan": "a4b8039ce8c93ab00867ef6b7e888822c09f4369",
              "versionType": "git",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV40": [
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        "type": "Secondary",
        "cvssData": {
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          "baseScore": 8.7,
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          "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"
        }
      }
    ],
    "cvssMetricV31": [
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        "source": "[email protected]",
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          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "availabilityImpact": "HIGH"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-05-11T18:56:19.590262Z",
          "id": "CVE-2026-7790",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
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              "technicalImpact": "partial"
            }
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          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
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  "weaknesses": [
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary",
      "description": [
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          "lang": "en",
          "value": "CWE-400"
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  "configurations": [
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          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
              "criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "0.6.0",
              "versionEndExcluding": "2.16.1",
              "matchCriteriaId": "F6362B55-F0FF-4196-984D-99512487861D"
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          ]
        }
      ]
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  ],
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-7790.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
        "Third Party Advisory"
      ]
    },
    {
      "url": "https://github.com/ninenines/cowlib/commit/a4b8039ce8c93ab00867ef6b7e888822c09f4369",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-7790",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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}