Node.js versions before 10.23.1, 12.20.1, 14.15.4, 15.5.1 allow two copies of a header field in an HTTP request (for example, two Transfer-Encoding header fields). In this case, Node.js identifies the first header field and ignores the second. This can lead to HTTP Request Smuggling.
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
https://hackerone.com/reports/1002188
https://lists.debian.org/debian-lts-announce/2022/12/msg00009.html
https://security.gentoo.org/glsa/202101-07
https://security.netapp.com/advisory/ntap-20210212-0003/