modules:
  - module: std
    versions:
      - fixed: 1.15.13
      - introduced: 1.16.0
        fixed: 1.16.5
    packages:
      - package: net/http/httputil
        symbols:
          - ReverseProxy.ServeHTTP
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.
published: 2022-02-17T17:33:16Z
cves:
  - CVE-2021-33197
credit: Mattias Grenfeldt (https://grenfeldt.dev) and Asta Olofsson
references:
  - fix: https://go.dev/cl/321929
  - fix: https://go.googlesource.com/go/+/950fa11c4cb01a145bb07eeb167d90a1846061b3
  - web: https://groups.google.com/g/golang-announce/c/RgCMkAEQjSI
  - report: https://go.dev/issue/46313