HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2_CVE-2026-43966

{
    "lastseen": "",
    "description": "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.\n\ncow_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.\n\nThis issue affects cowlib from 2.9.0.",
    "published": "2026-06-08T16:34:33.364Z",
    "modified": "2026-06-08T16:38:17.405Z",
    "type": "cve",
    "title": "HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2",
    "source": "EEF",
    "references": "https://cna.erlef.org/cves/CVE-2026-43966.html\nhttps://osv.dev/vulnerability/EEF-CVE-2026-43966\nhttps://github.com/ninenines/cowboy/commit/f77cb9b5e730e300fffb551db1ba5d1c4ed878ef\nhttps://github.com/ninenines/gun/commit/4f35609eb37109b106a863fc9ba83d7ee64e3e42",
    "id": "CVE-2026-43966",
    "bulletinFamily": "",
    "cwe": [
        "CWE-113"
    ],
    "cvelist": null,
    "sourceData": "ninenines cowlib 2.9.0\nninenines cowlib a8b793db3d6ffe91d62f81baf41b1dab4cd78fb6",
    "sourceHref": "",
    "cvss": {
        "score": 6.3,
        "severity": "MEDIUM",
        "vector": "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",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "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
}