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.
CVSS
No CVSS.
References
Configurations
No configuration.
History
08 Jun 2026, 17:16
| Type | Values Removed | Values Added |
|---|---|---|
| References | () https://github.com/wojtekmach/req/security/advisories/GHSA-px9f-whj3-246m - |
08 Jun 2026, 16:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-06-08 16:16
Updated : 2026-06-08 17:16
NVD link : CVE-2026-49756
Mitre link : CVE-2026-49756
CVE.ORG link : CVE-2026-49756
JSON object : View
Products Affected
No product.
CWE
CWE-93
Improper Neutralization of CRLF Sequences ('CRLF Injection')