module: std
package: net/http/httputil
versions:
- fixed: go1.15.13
- fixed: go1.16.5
- fixed: go1.17.0
description: |
  ReverseProxy can be made to forward certain hop-by-hop headers,
  including Connection. If the target of the ReverseProxy is
  itself a reverse proxy, this lets an attacker drop arbitrary
  headers, including those set by the ReverseProxy.Director.
cves:
- CVE-2021-33197
credit: Mattias Grenfeldt (https://grenfeldt.dev) and Asta Olofsson
symbols:
- ReverseProxy.ServeHTTP
links:
  pr: https://go.dev/cl/321929
  commit: https://go.googlesource.com/go/+/950fa11c4cb01a145bb07eeb167d90a1846061b3
  context:
  - https://groups.google.com/g/golang-announce/c/RgCMkAEQjSI
  - https://go.dev/issue/46313