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EUVD-2026-375454

fkie_cve-2026-48596

Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in elixir-tesla tesla allows HTTP header injection via Tesla.Multipart.add_content_type_param/2.

Tesla.Multipart.add_content_type_param/2 appends caller-supplied strings to the multipart content_type_params list without validating for CR (\r) or LF (\n) characters. Tesla.Multipart.headers/1 then joins these params verbatim with "; " to construct the outgoing Content-Type header value. A param containing \r\n splits the header line, allowing arbitrary headers to be injected into the outbound HTTP request. Any application that forwards untrusted input (such as a user-supplied charset or parameter string) into add_content_type_param/2 is affected.

This issue affects tesla: from 0.8.0 before 1.18.3.

GHSA-q7jx-v53g-848w — Tesla has CRLF injection in request `Content-Type` header via `add_content_type_param`

Affected: Hex: tesla

### Summary

`Tesla.Multipart.add_content_type_param/2` appends caller-supplied strings to the multipart `Content-Type` header with no validation. A param value containing `\r\n` splits the header line, allowing an attacker who controls any content-type parameter (charset, boundary parameter, etc.) to inject arbitrary headers into the outbound HTTP request.

### Details

`add_content_type_param/2` in `lib/tesla/multipart.ex` stores the supplied string directly in `multipart.content_type_params` without any CR/LF check. `headers/1` then joins all params with `"; "` and appends the result verbatim to the `Content-Type` header value. Because HTTP headers are delimited by `\r\n`, a param containing that sequence breaks out of the header field and introduces new header lines before the adapter writes the request to the socket.

The precondition is that untrusted input reaches `add_content_type_param/2`, which is the normal pattern for applications that accept user-supplied charset values, file type parameters, or any other content-type extension fields.

### PoC

1. Call `Tesla.Multipart.add_content_type_param/2` with a value containing `\r\nX-Injected: pwned`. 2. Pass the resulting `Multipart` struct as the request body via any Tesla adapter. 3. The raw request on the wire contains `X-Injected: pwned` as a standalone header line.

### Impact

Low severity (CVSS v4.0: 2.1). Any application using `tesla` 0.8.0 through 1.18.2 that passes untrusted input into `Tesla.Multipart.add_co…