wojtekmach req up to 0.5.x lib/req/utils.ex crlf injection

Summaryinfo

A vulnerability described as critical has been identified in wojtekmach req up to 0.5.x. This affects an unknown function in the library lib/req/utils.ex. The manipulation results in crlf injection. This vulnerability is cataloged as CVE-2026-49756. The attack must be initiated from a local position. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical has been found in wojtekmach req up to 0.5.x. Affected is an unknown code block in the library lib/req/utils.ex. The manipulation with an unknown input leads to a crlf injection vulnerability. CWE is classifying the issue as CWE-93. The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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-- 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.

The weakness was shared by Peter Ullrich and Jonatan Männchen. The advisory is available at github.com. This vulnerability is traded as CVE-2026-49756 since 06/01/2026. The exploitability is told to be easy. Local access is required to approach this attack. Technical details are known, but there is no available exploit.

Upgrading to version 0.6.0 eliminates this vulnerability. Applying the patch 74506ff2c5addf74df85d79dc726e9b2e264a8ba is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-35096). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Vendor

• wojtekmach

Name

• req

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5

Website

• Product: https://github.com/wojtekmach/req/

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If you want to get best quality of vulnerability data, you may have to visit VulDB.

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