Vulnerability in req (CVE-2026-49756)
Summary
Vulnerability in req (CVE-2026-49756). Risk of unauthorized operations or information disclosure. Exploitable via name. Mitigation: upgrade to 0.6.0 or later.
Original description
The description as published by the source.
Summary
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.
Workarounds
Sanitize attacker-influenced name, filename, and content_type values before passing them to Req.post/2 with form_multipart:. At minimum, reject (or strip) any value containing \r, \n, or ". When forwarding uploads, derive filename from a normalise…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-49756 has been found in req.
Attackers can target a specific entry point like name over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: upgrade req to 0.6.0 or later.
If unsure, ask your IT team or search "req CVE-2026-49756" on the vendor's site.
CVE-2026-49756 (req) — CWE-93 / CVSS v3 3.7
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: name / filename / content_type / value
Patched: 0.6.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-93) exists in req. Attackers reach the vulnerable code path via name without authentication.
Check the vendor advisory for the affected versions of req. Attack surface: name / filename / content_type / value.
Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.
Update to 0.6.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'req' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'req' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
reqを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade req to 0.6.0ステージング環境で 0.6.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- package hex.pm
- package github.com
- patch github.com
- web cna.erlef.org
- web osv.dev
- web github.com
- web github.com