https://github.com/python/cpython/commit/551f8e16f8bb38a1e9c6df259a2a0969493de070 commit: 551f8e16f8bb38a1e9c6df259a2a0969493de070 branch: main author: Serhiy Storchaka <[email protected]> committer: serhiy-storchaka <[email protected]> date: 2026-06-19T08:38:15Z summary:
gh-151695: Fix use-after-free of the curses screen encoding (GH-151696) The module-global curses_screen_encoding stored a borrowed pointer to the encoding owned by the window returned by the first initscr() call. That window can be deallocated while unctrl() and ungetch(), which have no window of their own, still use the pointer to encode non-ASCII characters. Keep a private copy of the encoding instead. Co-authored-by: Claude Opus 4.8 (1M context) <[email protected]> files: A Misc/NEWS.d/next/Library/2026-06-19-07-26-20.gh-issue-151695.IBDlkN.rst M Modules/_cursesmodule.c diff --git a/Misc/NEWS.d/next/Library/2026-06-19-07-26-20.gh-issue-151695.IBDlkN.rst b/Misc/NEWS.d/next/Library/2026-06-19-07-26-20.gh-issue-151695.IBDlkN.rst new file mode 100644 index 00000000000000..f44cb6b9307165 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-06-19-07-26-20.gh-issue-151695.IBDlkN.rst @@ -0,0 +1,4 @@ +Fix a use-after-free in the :mod:`curses` module. The encoding of the initial +screen, used by :func:`curses.unctrl` and :func:`curses.ungetch` to encode +non-ASCII characters, is now kept as a private copy instead of a borrowed +pointer to a window object that may be deallocated. diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c index 01cb6786e88aec..02a8e2c1b1bc10 100644 --- a/Modules/_cursesmodule.c +++ b/Modules/_cursesmodule.c @@ -208,7 +208,11 @@ static int curses_initscr_called = FALSE; /* Tells whether start_color() has been called to initialise color usage. */ static int curses_start_color_called = FALSE; -static const char *curses_screen_encoding = NULL; +/* Encoding of the initial screen, used by module-level functions that have + no window object to take it from (e.g. unctrl(), ungetch()). This is a + private copy: the window object that initscr() returns may be deallocated + while these functions are still in use. */ +static char *curses_screen_encoding = NULL; /* Utility Error Procedures */ @@ -3799,6 +3803,21 @@ _curses_init_pair_impl(PyObject *module, int pair_number, int fg, int bg) Py_RETURN_NONE; } +/* Refresh the private copy of the screen encoding from a freshly created + stdscr window object. Returns 0 on success, -1 with an exception set. */ +static int +curses_update_screen_encoding(PyObject *winobj) +{ + char *copy = _PyMem_Strdup(((PyCursesWindowObject *)winobj)->encoding); + if (copy == NULL) { + PyErr_NoMemory(); + return -1; + } + PyMem_Free(curses_screen_encoding); + curses_screen_encoding = copy; + return 0; +} + /*[clinic input] _curses.initscr @@ -3820,7 +3839,15 @@ _curses_initscr_impl(PyObject *module) _curses_set_null_error(state, "wrefresh", "initscr"); return NULL; } - return PyCursesWindow_New(state, stdscr, NULL, NULL); + PyObject *winobj = PyCursesWindow_New(state, stdscr, NULL, NULL); + if (winobj == NULL) { + return NULL; + } + if (curses_update_screen_encoding(winobj) < 0) { + Py_DECREF(winobj); + return NULL; + } + return winobj; } win = initscr(); @@ -3927,7 +3954,10 @@ _curses_initscr_impl(PyObject *module) if (winobj == NULL) { return NULL; } - curses_screen_encoding = ((PyCursesWindowObject *)winobj)->encoding; + if (curses_update_screen_encoding(winobj) < 0) { + Py_DECREF(winobj); + return NULL; + } return winobj; } @@ -5480,6 +5510,8 @@ static void cursesmodule_free(void *mod) { (void)cursesmodule_clear((PyObject *)mod); + PyMem_Free(curses_screen_encoding); + curses_screen_encoding = NULL; curses_module_loaded = 0; // allow reloading once garbage-collected } _______________________________________________ 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]
