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CVE-2026-43968

Full vulnerability record from the local CVENow database.

Description

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows SSE event splitting and injection via unvalidated field values. cow_sse:event/1 in cowlib guards the id and event fields against \n but not against bare \r, and the internal prefix_lines/2 function used for data and comment fields splits only on \n. Because the SSE specification requires decoders to treat \r\n, \r, and \n as equivalent line terminators, an attacker who controls any of these fields can inject additional SSE lines and forge a complete event with an arbitrary event type and data payload on the receiving end. In typical deployments where browser EventSource clients or other SSE consumers dispatch on event.type and render event.data, this enables event splitting, client-side logic manipulation, and stored-XSS-equivalent behaviour when event data is inserted into the DOM. This issue affects cowlib from 2.6.0 before 2.16.1.

Severity
MEDIUM
CVSS score
6.3 (v4.0)
Vulnerability status
Analyzed
Source identifier
6b3ad84c-e1a6-4bf7-a703-f496b71e49db
Published
2026-05-11 19:16:25.100000
Last modified
2026-10-26 18:10:00.173000
View original CVE JSON 
{
  "id": "CVE-2026-43968",
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "published": "2026-05-11T19:16:25.100",
  "lastModified": "2026-10-26T18:10:00.173",
  "vulnStatus": "Analyzed",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows SSE event splitting and injection via unvalidated field values.\n\ncow_sse:event/1 in cowlib guards the id and event fields against \\n but not against bare \\r, and the internal prefix_lines/2 function used for data and comment fields splits only on \\n. Because the SSE specification requires decoders to treat \\r\\n, \\r, and \\n as equivalent line terminators, an attacker who controls any of these fields can inject additional SSE lines and forge a complete event with an arbitrary event type and data payload on the receiving end. In typical deployments where browser EventSource clients or other SSE consumers dispatch on event.type and render event.data, this enables event splitting, client-side logic manipulation, and stored-XSS-equivalent behaviour when event data is inserted into the DOM.\n\nThis issue affects cowlib from 2.6.0 before 2.16.1."
    },
    {
      "lang": "es",
      "value": "La vulnerabilidad de Neutralización Incorrecta de Secuencias CRLF (’Inyección CRLF’) en ninenines cowlib permite la división e inyección de eventos SSE a través de valores de campo no validados.\n\ncow_sse:event/1 en cowlib protege los campos id y event contra \\n pero no contra un \\r desnudo, y la función interna prefix_lines/2 utilizada para los campos de datos y comentarios divide solo en \\n. Debido a que la especificación SSE requiere que los decodificadores traten \\r\\n, \\r y \\n como terminadores de línea equivalentes, un atacante que controla cualquiera de estos campos puede inyectar líneas SSE adicionales y falsificar un evento completo con un tipo de evento y una carga útil de datos arbitrarios en el extremo receptor. En implementaciones típicas donde los clientes EventSource del navegador u otros consumidores SSE despachan en event.type y renderizan event.data, esto permite la división de eventos, la manipulación de la lógica del lado del cliente y un comportamiento equivalente a XSS almacenado cuando los datos del evento se insertan en el DOM.\n\nEste problema afecta a cowlib a partir de 2.6.0."
    }
  ],
  "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_sse"
          ],
          "programFiles": [
            "src/cow_sse.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_sse:event/1"
            },
            {
              "name": "cow_sse:event_id/1"
            },
            {
              "name": "cow_sse:event_name/1"
            },
            {
              "name": "cow_sse:event_data/1"
            },
            {
              "name": "cow_sse:event_comment/1"
            },
            {
              "name": "cow_sse:prefix_lines/2"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:hex/cowlib",
          "versions": [
            {
              "version": "2.6.0",
              "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_sse"
          ],
          "programFiles": [
            "src/cow_sse.erl"
          ],
          "programRoutines": [
            {
              "name": "cow_sse:event/1"
            },
            {
              "name": "cow_sse:event_id/1"
            },
            {
              "name": "cow_sse:event_name/1"
            },
            {
              "name": "cow_sse:event_data/1"
            },
            {
              "name": "cow_sse:event_comment/1"
            },
            {
              "name": "cow_sse:prefix_lines/2"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "packageURL": "pkg:github/ninenines/cowlib",
          "versions": [
            {
              "version": "93b2b897cde238506c803faad4d1602d79dba7c9",
              "lessThan": "6165fc40efa159ba1cceee7e7981e790acba5d9c",
              "versionType": "git",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
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        "type": "Secondary",
        "cvssData": {
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          "attackRequirements": "PRESENT",
          "privilegesRequired": "NONE",
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          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "vulnAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "LOW",
          "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]",
        "type": "Primary",
        "cvssData": {
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          "baseSeverity": "MEDIUM",
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          "attackComplexity": "HIGH",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "CHANGED",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 1.4
      }
    ],
    "ssvcV203": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-05-11T18:57:13.541982Z",
          "id": "CVE-2026-43968",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
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              "technicalImpact": "partial"
            }
          ],
          "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": [
        {
          "lang": "en",
          "value": "CWE-93"
        }
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  "configurations": [
    {
      "nodes": [
        {
          "operator": "OR",
          "negate": false,
          "cpeMatch": [
            {
              "vulnerable": true,
              "criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*",
              "versionStartIncluding": "2.6.0",
              "versionEndExcluding": "2.16.1",
              "matchCriteriaId": "481B089B-8D5C-40D8-B1F0-4E543F63F602"
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  ],
  "references": [
    {
      "url": "https://cna.erlef.org/cves/CVE-2026-43968.html",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
        "Vendor Advisory"
      ]
    },
    {
      "url": "https://github.com/ninenines/cowlib/commit/6165fc40efa159ba1cceee7e7981e790acba5d9c",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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    {
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-43968",
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "tags": [
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}