{"id":"CVE-2026-39807","summary":"Client-supplied URI scheme trusted without transport verification in bandit","details":"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→HTTPS 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.","aliases":["EEF-CVE-2026-39807","GHSA-375f-4r2h-f99j"],"modified":"2026-07-08T08:13:03.234086494Z","published":"2026-05-01T20:34:22.832Z","database_specific":{"cwe_ids":["CWE-807"],"cna_assigner":"EEF","unresolved_ranges":[{"extracted_events":[{"introduced":"ff2f829326cd5dcf7335939aef9775269d881e28"},{"fixed":"45feea20dea8af7ffd7245271107b695c040e667"}],"source":"AFFECTED_FIELD"}],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39807.json"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-39807.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-39807"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39807.json"},{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-375f-4r2h-f99j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39807"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/45feea20dea8af7ffd7245271107b695c040e667"},{"type":"PACKAGE","url":"https://github.com/mtrudel/bandit"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mtrudel/bandit","events":[{"introduced":"124d697c3c604aca9122332a4ea789561b925f2e"},{"fixed":"e62619895d0d2584d7ffa57d43ef6f72437dfaff"},{"fixed":"45feea20dea8af7ffd7245271107b695c040e667"}],"database_specific":{"extracted_events":[{"introduced":"1.0.0"},{"fixed":"1.11.0"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["1.10.4","1.10.3","1.10.2","1.10.1","1.10.0","1.9.0","1.8.0","1.7.0","1.6.11","1.6.10","1.6.9","1.6.8","1.6.7","1.6.6","1.6.5","1.6.4","1.6.3","1.6.2","1.6.1","1.6.0","1.5.7","1.5.6","1.5.5","1.5.4","1.5.3","1.5.2","1.5.1","1.5.0","1.4.2","1.4.1","1.4.0","1.3.0","1.2.3","1.2.0","1.1.3","1.1.2","1.1.1","1.1.0","1.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-39807.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"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"}]}