Client-supplied URI scheme trusted without transport verification in bandit_CVE-2026-39807

{
    "lastseen": "",
    "description": "Reliance on Untrusted Inputs in a Security Decision vulnerability in mtrudel bandit allows unauthenticated transport-state spoofing on plaintext HTTP connections.\n\n'Elixir.Bandit.Pipeline':determine_scheme/2 in lib/bandit/pipeline.ex returns the client-supplied URI scheme verbatim, ignoring the transport's secure? flag. HTTP/1.1 absolute-form request targets (e.g. GET https://victim/path HTTP/1.1) and the HTTP/2 :scheme pseudo-header are both attacker-controlled strings that flow through this function. Over a plaintext TCP connection, a client can declare https and Bandit will set conn.scheme = :https even though no TLS was negotiated.\n\nDownstream Plug consumers that branch on conn.scheme are silently misled: Plug.SSL's already-secure branch skips its HTTP\u2192HTTPS redirect, cookies emitted with secure: true are sent over plaintext, audit logs record requests as having arrived over HTTPS, and CSRF/SameSite gating may make incorrect decisions.\n\nThis issue affects bandit: from 1.0.0 before 1.11.0.",
    "published": "2026-05-01T20:34:22.832Z",
    "modified": "2026-05-01T20:34:22.832Z",
    "type": "cve",
    "title": "Client-supplied URI scheme trusted without transport verification in bandit",
    "source": "EEF",
    "references": "https://github.com/mtrudel/bandit/security/advisories/GHSA-375f-4r2h-f99j\nhttps://cna.erlef.org/cves/CVE-2026-39807.html\nhttps://osv.dev/vulnerability/EEF-CVE-2026-39807\nhttps://github.com/mtrudel/bandit/commit/45feea20dea8af7ffd7245271107b695c040e667",
    "id": "CVE-2026-39807",
    "bulletinFamily": "",
    "cwe": [
        "CWE-807"
    ],
    "cvelist": null,
    "sourceData": "mtrudel bandit 1.0.0\nmtrudel bandit ff2f829326cd5dcf7335939aef9775269d881e28",
    "sourceHref": "",
    "cvss": {
        "score": 6.3,
        "severity": "MEDIUM",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/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": "bandit",
    "version": "1.0.0",
    "vendor": "mtrudel",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}