From 86ce2e05dc3ab07e1767444affd35c94a46cdb94 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Mon, 27 Apr 2026 03:49:27 +0200
Subject: [PATCH] [3.14] Document that multiprocessing treats local same-user
 processes as trusted (GH-149001) (#149033)

Document that multiprocessing treats local same-user processes as trusted (GH-149001)

Clarify in the Authentication keys section that the authkey handshake
covers Listener/Client (addressable endpoints) only, not the anonymous
pipes behind Pipe() and Queue, and that isolation between same-user
processes must be arranged at the OS level.
(cherry picked from commit f27e91e37212f148b8fe72a3656a69b242625622)

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
---
 Doc/library/multiprocessing.rst | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index d07612a885f..cc32a76c584 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -2907,6 +2907,16 @@ between themselves.
 
 Suitable authentication keys can also be generated by using :func:`os.urandom`.
 
+This authentication protects :class:`Listener` and :func:`Client` connections,
+which are reachable by address.  It is not applied to the anonymous pipes
+created by :func:`~multiprocessing.Pipe` or used internally by
+:class:`~multiprocessing.Queue`.
+:mod:`multiprocessing` treats all local processes running as the same user as
+trusted; on most operating systems such processes can access each other's pipe
+file descriptors regardless.  Applications that require isolation between
+processes of the same user must arrange it at the operating-system level --
+for example, by running workers under a different user account or in a sandbox.
+
 
 Logging
 ^^^^^^^