The package github.com/pires/go-proxyproto before 0.5.0 are vulnerable to Denial of Service (DoS) via the parseVersion1() function. The reader in this package is a default bufio.Reader wrapping a net.Conn. It will read from the connection until it finds a newline. Since no limits are implemented in the code, a deliberately malformed V1 header could be used to exhaust memory in a server process using this code - and create a DoS. This can be exploited by sending a stream starting with PROXY and continuing to send data (which does not contain a newline) until the target stops acknowledging. The risk here is small, because only trusted sources should be allowed to send proxy protocol headers.
https://snyk.io/vuln/SNYK-GOLANG-GITHUBCOMPIRESGOPROXYPROTO-1081577
https://github.com/pires/go-proxyproto/pull/71
https://github.com/pires/go-proxyproto/issues/69
https://github.com/pires/go-proxyproto/commit/7f48261db810703d173f27f3309a808cc2b49b8b