{"cve":"CVE-2026-39807","nvd":{"published":"2026-05-01T21:16:17.180","modified":"2026-10-26T21:10:00.170","status":"Deferred","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→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.","cvss_v4":{"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","score":6.3},"cvss_v3":null,"cwes":["CWE-807"],"references":["https://cna.erlef.org/cves/CVE-2026-39807.html","https://github.com/mtrudel/bandit/commit/45feea20dea8af7ffd7245271107b695c040e667","https://github.com/mtrudel/bandit/security/advisories/GHSA-375f-4r2h-f99j","https://osv.dev/vulnerability/EEF-CVE-2026-39807","https://github.com/mtrudel/bandit/security/advisories/GHSA-375f-4r2h-f99j"],"products":[],"source":"nvd","synced_at":"2026-10-26T21:38:48.864438205+00:00"},"epss":{"cve":"CVE-2026-39807","score":0.00454,"percentile":0.39142,"date":"2026-10-26"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}