AIKIDO-2026-535593
http-proxy-middleware is vulnerable to Improper Neutralization of CRLF Sequences ('CRLF Injection')
37
Low Risk
This Affects:
http-proxy-middlewareTL;DR
http-proxy-middleware previously serialized multipart/form-data using string concatenation from user-controlled inputs (boundary, field names, field values). This enabled CR/LF and multipart boundary delimiter injection to smuggle additional multipart parts/headers through the proxy request. The fix adds strict validation and escaping in stringifyFormData and fails closed (proxy request is destroyed) when invalid multipart content is detected, returning HTTP 400.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and configure the router option as an object mapping hosts or host+path keys to upstream targets.
Background info
http-proxy-middleware is vulnerable to Improper Neutralization of CRLF Sequences ('CRLF Injection') in versions 3.0.0 - 3.0.6 and 4.0.0 - 4.1.0.
How to fix this
Upgrade the http-proxy-middleware library to the patch version.
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SOC 2Compliant
ISO 27001Compliant