Mend.io Vulnerability Database
The largest open source vulnerability database
What is a Vulnerability ID?
New vulnerability? Tell us about it!
CVE-2026-49756
Published:June 08, 2026
Updated:August 04, 2026
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.
Affected Packages
https://github.com/wojtekmach/req.git (GITHUB):
Affected version(s) >=v0.1.0 <v0.6.1
Fix Suggestion:
Update to version v0.6.1
req (HEX):
Affected version(s) >=0.5.3 <0.6.0
Fix Suggestion:
Update to version 0.6.0
req (HEX):
Affected version(s) >=0.5.3 <0.6.0
Fix Suggestion:
Update to version 0.6.0
Do you need more information?
Contact Us
CVSS v4
Base Score:
2.1
Attack Vector
LOCAL
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
LOW
Subsequent System Integrity
LOW
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improper Neutralization of CRLF Sequences ('CRLF Injection')
EPSS
Base Score:
0.18