{"affected":[{"package":{"ecosystem":"Hex","name":"bandit","purl":"pkg:hex/bandit"},"ranges":[{"events":[{"introduced":"1.0.0"},{"fixed":"1.11.0"}],"type":"SEMVER"}],"versions":["1.0.0","1.1.0","1.1.1","1.1.2","1.1.3","1.2.0","1.2.1","1.2.2","1.2.3","1.3.0","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.6.0","1.6.1","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.6.10","1.6.11","1.7.0","1.8.0","1.9.0","1.10.0","1.10.1","1.10.2","1.10.3","1.10.4"]},{"ranges":[{"events":[{"introduced":"ff2f829326cd5dcf7335939aef9775269d881e28"},{"fixed":"1.11.0"}],"repo":"https://github.com/mtrudel/bandit","type":"GIT"}]}],"aliases":["GHSA-375f-4r2h-f99j","CVE-2026-39807"],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Mat Trudel","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen","type":"ANALYST"}],"database_specific":{"capec_ids":["CAPEC-220"],"cpe_ids":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-807"]},"details":"## Summary\n\nReliance 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.\n\n## Configuration\n\nThe vulnerable system must be accepting plaintext (non-TLS) HTTP connections, either directly or via h2c. Deployments that exclusively use TLS are not affected.","id":"EEF-CVE-2026-39807","modified":"2026-05-01T20:34:22.832Z","published":"2026-05-01T20:34:22.832Z","references":[{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-375f-4r2h-f99j"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-39807.html"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/45feea20dea8af7ffd7245271107b695c040e667"},{"type":"PACKAGE","url":"https://hex.pm/packages/bandit"}],"related":[],"schema_version":"1.7.3","severity":[{"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","type":"CVSS_V4"}],"summary":"Client-supplied URI scheme trusted without transport verification in bandit","upstream":[]}