{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-43969",
        "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "state": "PUBLISHED",
        "assignerShortName": "EEF",
        "dateReserved": "2026-05-04T18:23:25.573Z",
        "datePublished": "2026-05-11T18:06:40.667Z",
        "dateUpdated": "2026-10-09T06:57:15.234Z"
    },
    "containers": {
        "cna": {
            "affected": [
                {
                    "collectionURL": "https://repo.hex.pm",
                    "cpes": [
                        "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "cow_cookie"
                    ],
                    "packageName": "cowlib",
                    "packageURL": "pkg:hex/cowlib",
                    "product": "cowlib",
                    "programFiles": [
                        "src/cow_cookie.erl"
                    ],
                    "programRoutines": [
                        {
                            "name": "cow_cookie:cookie/1"
                        }
                    ],
                    "repo": "https://github.com/ninenines/cowlib",
                    "vendor": "ninenines",
                    "versions": [
                        {
                            "lessThan": "2.21.0",
                            "status": "affected",
                            "version": "2.9.0",
                            "versionType": "semver"
                        }
                    ]
                },
                {
                    "collectionURL": "https://github.com",
                    "cpes": [
                        "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "cow_cookie"
                    ],
                    "packageName": "ninenines/cowlib",
                    "packageURL": "pkg:github/ninenines/cowlib",
                    "product": "cowlib",
                    "programFiles": [
                        "src/cow_cookie.erl"
                    ],
                    "programRoutines": [
                        {
                            "name": "cow_cookie:cookie/1"
                        }
                    ],
                    "repo": "https://github.com/ninenines/cowlib",
                    "vendor": "ninenines",
                    "versions": [
                        {
                            "lessThan": "c17fd73945ef536cccecc492d286fb6b6d1c3307",
                            "status": "affected",
                            "version": "f017f8a0ecbffd5033d9ab49bf180186f7a523a7",
                            "versionType": "git"
                        }
                    ]
                }
            ],
            "configurations": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>The application must pass attacker-controlled bytes as cookie names or values to <code>cow_cookie:cookie/1</code>. Applications that construct cookie lists exclusively from trusted, application-controlled values are not affected.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "The application must pass attacker-controlled bytes as cookie names or values to `cow_cookie:cookie/1`. Applications that construct cookie lists exclusively from trusted, application-controlled values are not affected."
                        }
                    ],
                    "value": "The application must pass attacker-controlled bytes as cookie names or values to cow_cookie:cookie/1. Applications that construct cookie lists exclusively from trusted, application-controlled values are not affected."
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "cpeMatch": [
                                {
                                    "criteria": "cpe:2.3:a:ninenines:cowlib:*:*:*:*:*:*:*:*",
                                    "versionEndExcluding": "2.21.0",
                                    "versionStartIncluding": "2.9.0",
                                    "vulnerable": true
                                }
                            ],
                            "negate": false,
                            "operator": "OR"
                        }
                    ],
                    "operator": "AND"
                }
            ],
            "credits": [
                {
                    "lang": "en",
                    "type": "finder",
                    "value": "Peter Ullrich"
                },
                {
                    "lang": "en",
                    "type": "remediation developer",
                    "value": "Loïc Hoguin"
                },
                {
                    "lang": "en",
                    "type": "coordinator",
                    "value": "Jonatan Männchen / EEF"
                }
            ],
            "descriptions": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>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.</p>\n<p><code>cow_cookie:cookie/1</code> in cowlib builds a client-side <code>Cookie:</code> 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 <code>;</code>, <code>,</code>, CR, LF, or TAB characters into the serialized header. This enables two classes of attack: cookie smuggling within a single header (e.g. injecting <code>; admin=1</code> 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 (<code>parse_cookie_name/1</code>, <code>parse_cookie_value/1</code>) and <code>setcookie/3</code> already validate and reject these characters; the encoder alone is missing the check.</p>\n<p>This issue affects cowlib: from 2.9.0 before 2.21.0.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "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\n`cow_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 before 2.21.0."
                        }
                    ],
                    "value": "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 before 2.21.0."
                }
            ],
            "impacts": [
                {
                    "capecId": "CAPEC-105",
                    "descriptions": [
                        {
                            "lang": "en",
                            "value": "CAPEC-105 HTTP Request Splitting"
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV4_0": {
                        "Automatable": "NOT_DEFINED",
                        "Recovery": "NOT_DEFINED",
                        "Safety": "NOT_DEFINED",
                        "attackComplexity": "LOW",
                        "attackRequirements": "PRESENT",
                        "attackVector": "LOCAL",
                        "baseScore": 2.1,
                        "baseSeverity": "LOW",
                        "privilegesRequired": "NONE",
                        "providerUrgency": "NOT_DEFINED",
                        "subAvailabilityImpact": "NONE",
                        "subConfidentialityImpact": "NONE",
                        "subIntegrityImpact": "LOW",
                        "userInteraction": "NONE",
                        "valueDensity": "NOT_DEFINED",
                        "vectorString": "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",
                        "version": "4.0",
                        "vulnAvailabilityImpact": "NONE",
                        "vulnConfidentialityImpact": "NONE",
                        "vulnIntegrityImpact": "LOW",
                        "vulnerabilityResponseEffort": "NOT_DEFINED"
                    },
                    "format": "CVSS",
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "GENERAL"
                        }
                    ]
                }
            ],
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-93",
                            "description": "CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')",
                            "lang": "en",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
                "shortName": "EEF",
                "dateUpdated": "2026-10-09T06:57:15.234Z"
            },
            "references": [
                {
                    "name": "GitHub Advisory",
                    "tags": [
                        "patch"
                    ],
                    "url": "https://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144"
                },
                {
                    "name": "EEF CNA record for CVE-2026-43969",
                    "tags": [
                        "related",
                        "third-party-advisory"
                    ],
                    "url": "https://cna.erlef.org/cves/CVE-2026-43969.html"
                },
                {
                    "name": "OSV record EEF-CVE-2026-43969",
                    "tags": [
                        "related"
                    ],
                    "url": "https://osv.dev/vulnerability/EEF-CVE-2026-43969"
                },
                {
                    "name": "Introducing commit f017f8a in ninenines/cowlib",
                    "tags": [
                        "related"
                    ],
                    "url": "https://github.com/ninenines/cowlib/commit/f017f8a0ecbffd5033d9ab49bf180186f7a523a7"
                },
                {
                    "name": "Fix commit c17fd73 in ninenines/cowlib",
                    "tags": [
                        "patch"
                    ],
                    "url": "https://github.com/ninenines/cowlib/commit/c17fd73945ef536cccecc492d286fb6b6d1c3307"
                }
            ],
            "source": {
                "discovery": "EXTERNAL"
            },
            "title": "Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1",
            "workarounds": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>Validate inputs into <code>cow_cookie:cookie/1</code> to only include valid cookie name and value characters as defined in RFC 6265 Section 4.1.1 before passing them to the function.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "Validate inputs into `cow_cookie:cookie/1` to only include valid cookie name and value characters as defined in RFC 6265 Section 4.1.1 before passing them to the function."
                        }
                    ],
                    "value": "Validate inputs into cow_cookie:cookie/1 to only include valid cookie name and value characters as defined in RFC 6265 Section 4.1.1 before passing them to the function."
                }
            ]
        },
        "adp": [
            {
                "metrics": [
                    {
                        "other": {
                            "type": "ssvc",
                            "content": {
                                "timestamp": "2026-05-11T18:55:16.028478Z",
                                "id": "CVE-2026-43969",
                                "options": [
                                    {
                                        "Exploitation": "none"
                                    },
                                    {
                                        "Automatable": "no"
                                    },
                                    {
                                        "Technical Impact": "partial"
                                    }
                                ],
                                "role": "CISA Coordinator",
                                "version": "2.0.3"
                            }
                        }
                    }
                ],
                "title": "CISA ADP Vulnrichment",
                "providerMetadata": {
                    "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
                    "shortName": "CISA-ADP",
                    "dateUpdated": "2026-05-11T18:55:26.121Z"
                }
            }
        ]
    }
}