CVE-2026-39807— Client-supplied URI scheme trusted without transport verification in bandit
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I. Basic Information for CVE-2026-39807
Vulnerability Information
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Vulnerability Title
Client-supplied URI scheme trusted without transport verification in bandit
Source: NVD (National Vulnerability Database)
Vulnerability Description
Reliance on Untrusted Inputs in a Security Decision vulnerability in mtrudel bandit allows unauthenticated transport-state spoofing on plaintext HTTP connections. '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. Downstream 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. This issue affects bandit: from 1.0.0 before 1.11.0.
Source: NVD (National Vulnerability Database)
CVSS Information
N/A
Source: NVD (National Vulnerability Database)
Vulnerability Type
在安全决策中依赖未经信任的输入
Source: NVD (National Vulnerability Database)
Vulnerability Title
Bandit 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Bandit是Mat Trudel个人开发者的一款高性能HTTP与WebSocket服务器。 Bandit 1.0.0版本至1.11.0之前版本存在安全漏洞，该漏洞源于依赖不可信输入进行安全决策，可能导致未经身份验证的攻击者在明文HTTP连接上伪造传输状态。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-39807
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Same Patch Batch · mtrudel · 2026-05-01 · 5 CVEs total
| CVE-2026-42788 | HTTP/2 frame size limit checked after body is buffered in bandit | |
| CVE-2026-42786 | WebSocket fragmented message reassembly unbounded in bandit | |
| CVE-2026-39805 | CL.CL HTTP request smuggling via duplicate Content-Length in bandit | |
| CVE-2026-39804 | WebSocket permessage-deflate inflate has no output-size cap in bandit |
IV. Related Vulnerabilities
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