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CVE-2026-49756— Multipart form-data header injection in Req via unescaped name/filename/content_type

Quick assessment

Affected
wojtekmach req
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

req是roc个人开发者的一个使用 Black Magic 的简单 Go HTTP 客户端。 Req 0.5.3版本至0.6.0之前版本存在注入漏洞，该漏洞源于CRLF序列中和不当，可能导致通过攻击者影响的部分元数据进行多部分参数走私。

AI Predicted 9.1 Difficulty: Easy EPSS 0.34% · P26

Affected Version Matrix 2

VendorProduct Version RangeStatus
wojtekmach req 0.5.3< 0.6.0 affected
60253dbe9436cb8e9c738f895032f2e87939b597< 74506ff2c5addf74df85d79dc726e9b2e264a8ba affected
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I. Basic Information for CVE-2026-49756

Vulnerability Information
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Vulnerability Title
Multipart form-data header injection in Req via unescaped name/filename/content_type
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
对CRLF序列的转义处理不恰当(CRLF注入)
Source: CVE Program / CVE List V5
Vulnerability Title
req 注入漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
req是roc个人开发者的一个使用 Black Magic 的简单 Go HTTP 客户端。 Req 0.5.3版本至0.6.0之前版本存在注入漏洞，该漏洞源于CRLF序列中和不当，可能导致通过攻击者影响的部分元数据进行多部分参数走私。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
wojtekmach req 0.5.3 ~ 0.6.0 cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*
wojtekmach req 60253dbe9436cb8e9c738f895032f2e87939b597 ~ 74506ff2c5addf74df85d79dc726e9b2e264a8ba cpe:2.3:a:wojtekmach:req:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-49756

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III. Intelligence Information for CVE-2026-49756

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Patches & Fixes for CVE-2026-49756 (1)

Vendor Advisories for CVE-2026-49756 (3)

IV. Related Vulnerabilities

Same product: req
Same vendor: wojtekmach
Same weakness: CWE-93

V. Comments for CVE-2026-49756

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