{"cve":"CVE-2026-49756","nvd":{"published":"2026-06-08T16:16:44.040","modified":"2026-08-18T19:15:38.860","status":"Analyzed","description":"Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata.\n\nReq.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.\n\nThis 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.\n\nThis issue affects req: from 0.5.3 before 0.6.0.","cvss_v4":{"vector":"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","score":2.1},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","score":3.7},"cwes":["CWE-93"],"references":["https://cna.erlef.org/cves/CVE-2026-49756.html","https://github.com/wojtekmach/req/commit/74506ff2c5addf74df85d79dc726e9b2e264a8ba","https://github.com/wojtekmach/req/security/advisories/GHSA-px9f-whj3-246m","https://osv.dev/vulnerability/EEF-CVE-2026-49756","https://github.com/wojtekmach/req/security/advisories/GHSA-px9f-whj3-246m"],"products":["wojtekmach:req"],"source":"nvd","synced_at":"2026-10-19T22:38:48.522727527+00:00"},"epss":{"cve":"CVE-2026-49756","score":0.00207,"percentile":0.10845,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}