Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1_CVE-2026-43969

{
    "lastseen": "",
    "description": "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.",
    "published": "2026-05-11T18:06:40.667Z",
    "modified": "2026-05-11T18:55:26.121Z",
    "type": "cve",
    "title": "Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1",
    "source": "EEF",
    "references": "https://cna.erlef.org/cves/CVE-2026-43969.html\nhttps://osv.dev/vulnerability/EEF-CVE-2026-43969\nhttps://github.com/erlef/cowlib/commit/177953dd51540da11090666c1f007214127a1144",
    "id": "CVE-2026-43969",
    "bulletinFamily": "",
    "cwe": [
        "CWE-93"
    ],
    "cvelist": null,
    "sourceData": "ninenines cowlib 2.9.0\nninenines cowlib f017f8a0ecbffd5033d9ab49bf180186f7a523a7",
    "sourceHref": "",
    "cvss": {
        "score": 2.1,
        "severity": "LOW",
        "vector": "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"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "cowlib",
    "version": "2.9.0",
    "vendor": "ninenines",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}