go1.21.4 (released 2023-11-07) includes security fixes to the path/filepath
package, as well as bug fixes to the linker, the runtime, the compiler, and
the go/types, net/http, and runtime/cgo packages. See the Go 1.21.4 milestone
on our issue tracker for details:

- https://github.com/golang/go/issues?q=milestone%3AGo1.21.4+label%3ACherryPickApproved
- full diff: golang/go@go1.21.3...go1.21.4

from the security mailing:

[security] Go 1.21.4 and Go 1.20.11 are released

Hello gophers,

We have just released Go versions 1.21.4 and 1.20.11, minor point releases.

These minor releases include 2 security fixes following the security policy:

- path/filepath: recognize `\??\` as a Root Local Device path prefix.

  On Windows, a path beginning with `\??\` is a Root Local Device path equivalent
  to a path beginning with `\\?\`. Paths with a `\??\` prefix may be used to
  access arbitrary locations on the system. For example, the path `\??\c:\x`
  is equivalent to the more common path c:\x.

  The filepath package did not recognize paths with a `\??\` prefix as special.

  Clean could convert a rooted path such as `\a\..\??\b` into
  the root local device path `\??\b`. It will now convert this
  path into `.\??\b`.

  `IsAbs` did not report paths beginning with `\??\` as absolute.
  It now does so.

  VolumeName now reports the `\??\` prefix as a volume name.

  `Join(`\`, `??`, `b`)` could convert a seemingly innocent
  sequence of path elements into the root local device path
  `\??\b`. It will now convert this to `\.\??\b`.

  This is CVE-2023-45283 and https://go.dev/issue/63713.

- path/filepath: recognize device names with trailing spaces and superscripts

  The `IsLocal` function did not correctly detect reserved names in some cases:

  - reserved names followed by spaces, such as "COM1 ".
  - "COM" or "LPT" followed by a superscript 1, 2, or 3.

  `IsLocal` now correctly reports these names as non-local.

  This is CVE-2023-45284 and https://go.dev/issue/63713.

Signed-off-by: Sebastiaan van Stijn <[email protected]>