ubuntu-cve-2026-43966
Vulnerability from osv_ubuntu
Published
2026-06-15 00:00
Modified
2026-06-17 08:57
Summary
Details

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values. cow_http_struct_hd:escape_string/2 in cowlib only escapes \ and ", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20–0x7E, excluding " and ), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \r\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting. This issue affects cowlib from 2.9.0.

Severity
6.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "3.5.7-1ubuntu0.16.04.4+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@3.5.7-1ubuntu0.16.04.4+esm2?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.5.4-1",
        "3.5.4-3",
        "3.5.4-3.1",
        "3.5.7-1",
        "3.5.7-1ubuntu0.16.04.1",
        "3.5.7-1ubuntu0.16.04.2",
        "3.5.7-1ubuntu0.16.04.4",
        "3.5.7-1ubuntu0.16.04.4+esm1",
        "3.5.7-1ubuntu0.16.04.4+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "3.6.10-1ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@3.6.10-1ubuntu0.5?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.6.10-1",
        "3.6.10-1ubuntu0.1",
        "3.6.10-1ubuntu0.3",
        "3.6.10-1ubuntu0.4",
        "3.6.10-1ubuntu0.5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "3.8.3-0ubuntu0.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@3.8.3-0ubuntu0.3?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.7.8-4ubuntu2",
        "3.7.18-1",
        "3.8.2-0ubuntu1",
        "3.8.2-0ubuntu1.1",
        "3.8.2-0ubuntu1.2",
        "3.8.2-0ubuntu1.3",
        "3.8.2-0ubuntu1.4",
        "3.8.2-0ubuntu1.5",
        "3.8.3-0ubuntu0.1",
        "3.8.3-0ubuntu0.2",
        "3.8.3-0ubuntu0.3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "3.9.27-0ubuntu0.2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@3.9.27-0ubuntu0.2?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.8.9-3ubuntu1",
        "3.9.8-1",
        "3.9.8-2",
        "3.9.8-3",
        "3.9.8-5",
        "3.9.8-6",
        "3.9.13-1",
        "3.9.13-1ubuntu0.22.04.1",
        "3.9.13-1ubuntu0.22.04.2",
        "3.9.27-0ubuntu0.1",
        "3.9.27-0ubuntu0.2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "3.12.1-1ubuntu1.4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@3.12.1-1ubuntu1.4?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.12.1-1",
        "3.12.1-1ubuntu1",
        "3.12.1-1ubuntu1.2",
        "3.12.1-1ubuntu1.4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "4.0.5-8ubuntu2.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@4.0.5-8ubuntu2.1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.5-2ubuntu2",
        "4.0.5-6ubuntu1",
        "4.0.5-8ubuntu1",
        "4.0.5-8ubuntu2",
        "4.0.5-8ubuntu2.1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "rabbitmq-server",
            "binary_version": "4.0.5-10ubuntu5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "rabbitmq-server",
        "purl": "pkg:deb/ubuntu/rabbitmq-server@4.0.5-10ubuntu5?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.0.5-8ubuntu2",
        "4.0.5-10ubuntu1",
        "4.0.5-10ubuntu2",
        "4.0.5-10ubuntu3",
        "4.0.5-10ubuntu4",
        "4.0.5-10ubuntu5"
      ]
    }
  ],
  "aliases": [],
  "details": "Improper Neutralization of CRLF Sequences in HTTP Headers (\u0027HTTP Request/Response Splitting\u0027) vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values. cow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20\u20130x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting. This issue affects cowlib from 2.9.0.",
  "id": "UBUNTU-CVE-2026-43966",
  "modified": "2026-06-17T08:57:56Z",
  "published": "2026-06-15T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-43966"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-43966"
    },
    {
      "type": "REPORT",
      "url": "https://cna.erlef.org/cves/CVE-2026-43966.html"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-43966"
  ],
  "withdrawn": "2026-06-19T15:57:11Z"
}



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