id: GO-2021-0241
modules:
    - module: std
      versions:
        - fixed: 1.15.13
        - introduced: 1.16.0-0
          fixed: 1.16.5
      vulnerable_at: 1.16.4
      packages:
        - package: net/http/httputil
          symbols:
            - ReverseProxy.ServeHTTP
          skip_fix: 'TODO: revisit this reason (fix appears to not work with Go <1.18)'
summary: Attacker can drop certain headers in net/http/httputil
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
credits:
    - Mattias Grenfeldt (https://grenfeldt.dev)
    - 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