{"id":"CVE-2026-39807","aliases":["EEF-CVE-2026-39807","GHSA-375f-4r2h-f99j"],"url":"https://o3.security/vulnerability/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.","published":"2026-05-01T20:34:22.832Z","modified":"2026-08-07T11:49:51.185281369Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"bandit","fixedVersion":"1.11.0"}],"fix":{"url":"https://github.com/mtrudel/bandit/commit/45feea20dea8af7ffd7245271107b695c040e667","label":"mtrudel/bandit@45feea2"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:49:51.185281369Z"}}