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EUVD-2026-324120

fkie_cve-2026-48861

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in elixir-mint Mint allows HTTP Request Splitting and HTTP Request Smuggling.

In lib/mint/http1/request.ex, the encode_request_line/2 function splices the caller-supplied method and target arguments directly into the HTTP/1 request line without any character validation: [method, ?\s, target, " HTTP/1.1\r\n"]. An application that forwards attacker-controlled input as the HTTP method or target to Mint.HTTP.request/5 is therefore exposed to request-line CRLF injection: the attacker can terminate the request line early, inject arbitrary headers, and smuggle an entirely separate pipelined HTTP request onto the same TCP connection.

Mint 1.7.0 introduced validate_request_target/2, which rejects CRLF and other control characters in the target by default and closes the path/query vector unless the caller opts out via skip_target_validation: true. The method field remains unvalidated, so the method-based injection is exploitable under the default Mint configuration on all versions.

This issue affects mint: from 0.1.0 before 1.9.0.

GHSA-2pg6-44cx-c49v — mint has potential CRLF injection in its HTTP request line via unvalidated `method`/`target`

Affected: Hex: mint

### Summary

Mint's HTTP/1 request encoder splices the caller-supplied `method` and `target` directly into the request line without character validation. An application that forwards attacker-controlled input as the HTTP method or the target to `Mint.HTTP.request/5` is exposed to request-line CRLF injection, allowing the attacker to terminate the request line early, inject arbitrary headers, and pipeline a fully attacker-chosen second request onto the same TCP connection.

### Details

`encode_request_line/2` in `lib/mint/http1/request.ex` writes `method` and `target` to the wire verbatim. `encode_headers/1` validates header names and values, but there is no equivalent `validate_method!/1`.

Mint 1.7.0 added `validate_request_target/2`, which rejects CRLF and other control characters in `target` by default and closes the path/query vector. The `method` field remains unvalidated, so a CRLF-bearing method such as `"GET / HTTP/1.1\r\nX-Smuggled: 1\r\nGET /admin"` is accepted and written to the socket as-is. Bytes after the first `\r\n` are interpreted by the peer as an injected header, or, with a second `\r\n`, as an additional pipelined request.

### PoC

1. Stand up a Mint-using gateway/proxy that calls `Mint.HTTP.request(conn, method, "/", [], nil)` with `method` taken from caller input. 2. Send a request whose forwarded method is `"GET / HTTP/1.1\r\nX-Smuggled-Header: pwned\r\nGET /admin/delete-everything"`. 3. Observe the bytes received by the upstream server: the smuggled…