From 98a91e929d506a0beb2c4f0adf9de354df72d28a Mon Sep 17 00:00:00 2001 From: Steve Dower Date: Wed, 17 Jun 2026 00:16:06 +0100 Subject: [PATCH] gh-151544: Fixes CVE-2026-12003 by removing the fallback to %VPATH%/Modules/Setup.local for discovering sources in getpath.py (GH-151545) (cherry picked from commit 9e863fab283eddca9c2a8f9d1ee30f4dc243e314) Co-authored-by: Steve Dower --- Makefile.pre.in | 2 ++ ...2026-06-16-14-58-02.gh-issue-151544._bexVy.rst | 4 ++++ Modules/getpath.py | 15 ++++----------- 3 files changed, 10 insertions(+), 11 deletions(-) create mode 100644 Misc/NEWS.d/next/Security/2026-06-16-14-58-02.gh-issue-151544._bexVy.rst diff --git a/Makefile.pre.in b/Makefile.pre.in index 81d4d50f82f008e..d59b5c56f3b3a5c 100644 --- a/Makefile.pre.in +++ b/Makefile.pre.in @@ -980,6 +980,8 @@ Programs/_bootstrap_python.o: Programs/_bootstrap_python.c $(BOOTSTRAP_HEADERS) _bootstrap_python: $(LIBRARY_OBJS_OMIT_FROZEN) Programs/_bootstrap_python.o Modules/getpath.o Modules/Setup.local $(LINKCC) $(PY_LDFLAGS_NOLTO) -o $@ $(LIBRARY_OBJS_OMIT_FROZEN) \ Programs/_bootstrap_python.o Modules/getpath.o $(LIBS) $(MODLIBS) $(SYSLIBS) + # Dummy pybuilddir.txt is needed for _bootstrap_python to be runnable + @echo "none" > ./pybuilddir.txt ############################################################################ diff --git a/Misc/NEWS.d/next/Security/2026-06-16-14-58-02.gh-issue-151544._bexVy.rst b/Misc/NEWS.d/next/Security/2026-06-16-14-58-02.gh-issue-151544._bexVy.rst new file mode 100644 index 000000000000000..418e3b4b9677943 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2026-06-16-14-58-02.gh-issue-151544._bexVy.rst @@ -0,0 +1,4 @@ +:file:`Modules/Setup.local` is no longer used as a landmark to discover +whether Python is running in a source tree, as it could potentially affect +actual installs. The :file:`pybuilddir.txt` file is now the sole indicator +of running in a source tree. diff --git a/Modules/getpath.py b/Modules/getpath.py index 74f918cf28e402b..a7dd7342d4d2685 100644 --- a/Modules/getpath.py +++ b/Modules/getpath.py @@ -128,8 +128,7 @@ # checked by looking for the BUILDDIR_TXT file, which contains the # relative path to the platlib dir. The executable_dir value is # derived from joining the VPATH preprocessor variable to the -# directory containing pybuilddir.txt. If it is not found, the -# BUILD_LANDMARK file is found, which is part of the source tree. +# directory containing pybuilddir.txt. # prefix is then found by searching up for a file that should only # exist in the source tree, and the stdlib dir is set to prefix/Lib. @@ -175,7 +174,6 @@ if os_name == 'posix' or os_name == 'darwin': BUILDDIR_TXT = 'pybuilddir.txt' - BUILD_LANDMARK = 'Modules/Setup.local' DEFAULT_PROGRAM_NAME = f'python{VERSION_MAJOR}' STDLIB_SUBDIR = f'{platlibdir}/python{VERSION_MAJOR}.{VERSION_MINOR}' STDLIB_LANDMARKS = [f'{STDLIB_SUBDIR}/os.py', f'{STDLIB_SUBDIR}/os.pyc'] @@ -188,7 +186,6 @@ elif os_name == 'nt': BUILDDIR_TXT = 'pybuilddir.txt' - BUILD_LANDMARK = f'{VPATH}\\Modules\\Setup.local' DEFAULT_PROGRAM_NAME = f'python' STDLIB_SUBDIR = 'Lib' STDLIB_LANDMARKS = [f'{STDLIB_SUBDIR}\\os.py', f'{STDLIB_SUBDIR}\\os.pyc'] @@ -495,13 +492,9 @@ def search_up(prefix, *landmarks, test=isfile): platstdlib_dir = real_executable_dir build_prefix = joinpath(real_executable_dir, VPATH) except (FileNotFoundError, PermissionError): - if isfile(joinpath(real_executable_dir, BUILD_LANDMARK)): - build_prefix = joinpath(real_executable_dir, VPATH) - if os_name == 'nt': - # QUIRK: Windows builds need platstdlib_dir to be the executable - # dir. Normally the builddir marker handles this, but in this - # case we need to correct manually. - platstdlib_dir = real_executable_dir + # We used to check for an alternate landmark here, but now we require + # BUILDDIR_TXT to exist. (gh-151544; CVE-2026-12003) + pass if build_prefix: if os_name == 'nt':