From d9ff6c86a785587a81d7c8e6cb89a3b9d7eea56b Mon Sep 17 00:00:00 2001 From: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> Date: Wed, 11 Mar 2026 12:29:43 +0000 Subject: [PATCH] Warn that overriding `__builtins__` for `eval` is not a security mechanism (GH-145773) (cherry picked from commit eb9ae65e5b1cdfcf4f60d36c0353c857bc27b92f) Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com> Co-authored-by: Ned Batchelder --- Doc/library/functions.rst | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst index ca12b65313b5e4..96b88b38039fa3 100644 --- a/Doc/library/functions.rst +++ b/Doc/library/functions.rst @@ -597,17 +597,18 @@ are always available. They are listed here in alphabetical order. .. warning:: This function executes arbitrary code. Calling it with - user-supplied input may lead to security vulnerabilities. + untrusted user-supplied input will lead to security vulnerabilities. The *source* argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the *globals* and *locals* mappings as global and local namespace. If the *globals* dictionary is present and does not contain a value for the key ``__builtins__``, a reference to the dictionary of the built-in module :mod:`builtins` is - inserted under that key before *source* is parsed. That way you can - control what builtins are available to the executed code by inserting your - own ``__builtins__`` dictionary into *globals* before passing it to - :func:`eval`. If the *locals* mapping is omitted it defaults to the + inserted under that key before *source* is parsed. + Overriding ``__builtins__`` can be used to restrict or change the available + names, but this is **not** a security mechanism: the executed code can + still access all builtins. + If the *locals* mapping is omitted it defaults to the *globals* dictionary. If both mappings are omitted, the source is executed with the *globals* and *locals* in the environment where :func:`eval` is called. Note, *eval()* will only have access to the @@ -658,7 +659,7 @@ are always available. They are listed here in alphabetical order. .. warning:: This function executes arbitrary code. Calling it with - user-supplied input may lead to security vulnerabilities. + untrusted user-supplied input will lead to security vulnerabilities. This function supports dynamic execution of Python code. *source* must be either a string or a code object. If it is a string, the string is parsed as @@ -689,9 +690,10 @@ are always available. They are listed here in alphabetical order. If the *globals* dictionary does not contain a value for the key ``__builtins__``, a reference to the dictionary of the built-in module - :mod:`builtins` is inserted under that key. That way you can control what - builtins are available to the executed code by inserting your own - ``__builtins__`` dictionary into *globals* before passing it to :func:`exec`. + :mod:`builtins` is inserted under that key. + Overriding ``__builtins__`` can be used to restrict or change the available + names, but this is **not** a security mechanism: the executed code can + still access all builtins. The *closure* argument specifies a closure--a tuple of cellvars. It's only valid when the *object* is a code object containing