https://github.com/python/cpython/commit/eb9ae65e5b1cdfcf4f60d36c0353c857bc27b92f commit: eb9ae65e5b1cdfcf4f60d36c0353c857bc27b92f branch: main author: Stan Ulbrych <[email protected]> committer: encukou <[email protected]> date: 2026-03-11T13:29:43+01:00 summary:
Warn that overriding `__builtins__` for `eval` is not a security mechanism (GH-145773) Co-authored-by: Ned Batchelder <[email protected]> files: M Doc/library/functions.rst diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst index 1d83cb6f2bb688..483e5b1d8fdba7 100644 --- a/Doc/library/functions.rst +++ b/Doc/library/functions.rst @@ -606,17 +606,18 @@ 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 @@ -671,7 +672,7 @@ 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 @@ -702,9 +703,10 @@ 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 _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
