CVE-2026-39805: Elixir Bandit Duplicate Header Smuggling

Extracting HTTP request headers such as 'content-length' using a function that only returns the first occurrence (like `List.keyfind`) ignores duplicates. This violates RFC 9112 §6.3 and can permit HTTP Request Smuggling. Instead of fetching the first match, filter all matching headers and reject the request if duplicates or conflicts are found.

Provally CuratedPublic repositoryHighMedium confidenceVerifiedApache-2.0Elixir
greprules fetch cve-2026-39805-elixir-bandit-duplicate-header-smuggling --engine opengrep

Description

Extracting HTTP request headers such as 'content-length' using a function that only returns the first occurrence (like `List.keyfind`) ignores duplicates. This violates RFC 9112 §6.3 and can permit HTTP Request Smuggling. Instead of fetching the first match, filter all matching headers and reject the request if duplicates or conflicts are found.