From 3f8cebf1273dfb6e081f2c0db256063bcdda4555 Mon Sep 17 00:00:00 2001
From: Vyron Vasileiadis <hi@fedonman.com>
Date: Sat, 17 Oct 2026 21:01:24 +0300
Subject: [PATCH 1/2] gh-155877: Reject a NUL cell in curses.complexstr() from
 an iterable

GH-156158 rejected a NUL in complexstr() given a str, but the iterable
path packed each item without that check, so the example from the issue
still built and addstr() dropped every cell after the NUL.
---
 Lib/test/test_curses.py |  2 ++
 Modules/_cursesmodule.c | 34 +++++++++++++++++++++++++++-------
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
index 5db44ebedd2ee0a..0eb43af795cdf80 100644
--- a/Lib/test/test_curses.py
+++ b/Lib/test/test_curses.py
@@ -1138,6 +1138,8 @@ def test_cell_null_char(self):
         # A string of cells cannot hold a NUL: it would end a batch write.
         self.assertRaises(ValueError, curses.complexstr, 'a\0b')
         self.assertRaises(ValueError, curses.complexstr, '\0')
+        self.assertRaises(ValueError, curses.complexstr, ['a', '\0', 'b'])
+        self.assertRaises(ValueError, curses.complexstr, [cell, 'b'])
 
     def test_add_string_behavior(self):
         # addstr() advances the cursor past the written text; addnstr()
diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
index 401b777be23caa6..a741b7754d0542e 100644
--- a/Modules/_cursesmodule.c
+++ b/Modules/_cursesmodule.c
@@ -1300,15 +1300,35 @@ curses_pack_cell(cursesmodule_state *state, PyObject *item, curses_cell_t *out)
 {
     if (Py_IS_TYPE(item, state->complexchar_type)) {
         *out = _PyCursesComplexCharObject_CAST(item)->cval;
-        return 0;
     }
-    if (PyUnicode_Check(item)) {
-        return curses_cell_pack(state, out, item, A_NORMAL, 0, "complexstr");
+    else if (PyUnicode_Check(item)) {
+        if (curses_cell_pack(state, out, item, A_NORMAL, 0, "complexstr") < 0) {
+            return -1;
+        }
     }
-    PyErr_Format(PyExc_TypeError,
-                 "complexstr cell must be a complexchar or a str, not %T",
-                 item);
-    return -1;
+    else {
+        PyErr_Format(PyExc_TypeError,
+                     "complexstr cell must be a complexchar or a str, not %T",
+                     item);
+        return -1;
+    }
+#ifdef HAVE_NCURSESW
+    wchar_t wstr[CCHARW_MAX + 1];
+    attr_t attr;
+    int pair;
+    if (curses_getcchar(out, wstr, &attr, &pair) == ERR) {
+        PyErr_SetString(state->error, "getcchar() returned ERR");
+        return -1;
+    }
+    int nul = wstr[0] == L'\0';
+#else
+    int nul = (*out & A_CHARTEXT) == 0;
+#endif
+    if (nul) {
+        PyErr_SetString(PyExc_ValueError, "embedded null character");
+        return -1;
+    }
+    return 0;
 }
 
 /* Wrap a buffer of len cells in a new complexstr, copying them in.  tp_alloc

From 4fc053424db0bfd7e76bebc4d70dad4ca129c216 Mon Sep 17 00:00:00 2001
From: Vyron Vasileiadis <hi@fedonman.com>
Date: Tue, 3 Nov 2026 17:54:01 +0200
Subject: [PATCH 2/2] Add a NEWS entry

---
 .../next/Library/2026-11-03-17-54-01.gh-issue-155877.KPDGNV.rst | 2 ++
 1 file changed, 2 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-11-03-17-54-01.gh-issue-155877.KPDGNV.rst

diff --git a/Misc/NEWS.d/next/Library/2026-11-03-17-54-01.gh-issue-155877.KPDGNV.rst b/Misc/NEWS.d/next/Library/2026-11-03-17-54-01.gh-issue-155877.KPDGNV.rst
new file mode 100644
index 000000000000000..93fc4954e52d1d7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-11-03-17-54-01.gh-issue-155877.KPDGNV.rst
@@ -0,0 +1,2 @@
+:class:`curses.complexstr` now rejects a NUL item in an iterable, as it
+already did for a NUL in a string.