{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.9.0"
              },
              {
                "last_affected": "2.9.0"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "b34155f725245848dca3a505398e262b1d50f25b"
            },
            {
              "fixed": "177953dd51540da11090666c1f007214127a1144"
            }
          ],
          "repo": "https://github.com/erlef/cowlib",
          "type": "GIT"
        },
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "2.9.0"
              },
              {
                "last_affected": "2.16.1"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "b34155f725245848dca3a505398e262b1d50f25b"
            },
            {
              "last_affected": "bae6b022af54566f3518a3aa59083b4591d552de"
            }
          ],
          "repo": "https://github.com/ninenines/cowlib",
          "type": "GIT"
        }
      ],
      "versions": [
        "2.9.0"
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-93"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43969.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "f017f8a0ecbffd5033d9ab49bf180186f7a523a7"
          },
          {
            "last_affected": "f017f8a0ecbffd5033d9ab49bf180186f7a523a7"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in ninenines cowlib allows HTTP request splitting and cookie smuggling via unvalidated cookie name and value fields.\n\ncow_cookie:cookie/1 in cowlib builds a client-side Cookie: request header from a list of name-value pairs without validating either field. An attacker who controls the cookie names or values passed to this function can inject ;, ,, CR, LF, or TAB characters into the serialized header. This enables two classes of attack: cookie smuggling within a single header (e.g. injecting \"; admin=1\" to introduce a phantom cookie that the receiving server treats as authentic) and HTTP request header splitting (injecting CRLF to append arbitrary headers or smuggle a complete second request against a shared upstream proxy). The decoder side (parse_cookie_name/1, parse_cookie_value/1) and setcookie/3 already validate and reject these characters; the encoder alone is missing the check.\n\nThis issue affects cowlib from 2.9.0.",
  "id": "CVE-2026-43969",
  "modified": "2026-07-08T05:39:11.154588905Z",
  "published": "2026-05-11T18:06:40.667Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-43969"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://cna.erlef.org/cves/CVE-2026-43969.html"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43969.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43969"
    },
    {
      "type": "FIX",
      "url": "https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ninenines/cowlib"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1"
}