Affected SwiftNIO systems are vulnerable to request smuggling attacks, in which they parse a given HTTP message differently from other network parties, potentially seeing a different number of requests than other servers. This can lead to failures of authentication, routing, and other issues.
This vulnerability can be found in the bundled copy of the Node.JS HTTP parser used in the NIOHTTP1
module.
No workaround is available, users must upgrade.
https://nodejs.org/en/blog/vulnerability/february-2020-security-releases/#http-request-smuggling-using-malformed-transfer-encoding-header-critical-cve-2019-15605