CVE-2026-49756
LowCVSS 3.7Exploitation Probability (EPSS)
Low risk11th percentile - higher than 11% of all known CVEs
Summary
The Req library (Elixir) versions 0.5.3 through 0.6.0 have a CRLF injection vulnerability. An attacker can manipulate multipart part metadata (e.g., filename) to inject headers and smuggle additional parts into the request sent to the downstream server.
Risk Assessment
The risk involves potential manipulation of HTTP requests sent by the application, leading to request smuggling attacks and integrity compromise.
Recommendation
Update the Req library to version 0.6.0 or later.
Original NVD description (English source)
Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata. Req.Utils.encode_form_part/2 in lib/req/utils.ex builds the per-part headers by interpolating the caller-supplied name, filename, and content_type values directly into the content-disposition and content-type lines with no escaping or CRLF stripping. A value containing ", \r, or \n closes the surrounding quoted value and starts a new header line; an additional \r\n--<boundary> terminates the current part and prepends a smuggled part of the attacker's choosing. This is reachable through every supported way of supplying a part. It is particularly easy when value is a %File.Stream{}, because filename then defaults to Path.basename(stream.path) and POSIX filenames may legitimately contain \r and \n. Any application that forwards user-controlled filenames (or field names / MIME types) through Req.post/2 with form_multipart: lets an attacker inject arbitrary headers into the outgoing multipart body or smuggle additional fields and parts into the request the victim service sends downstream. This issue affects req: from 0.5.3 before 0.6.0.