From a5eb798e0c67eb240e96978ebf9e79d4125c23e6 Mon Sep 17 00:00:00 2001
From: Brij <97006829+bkap123@users.noreply.github.com>
Date: Tue, 17 Mar 2026 15:20:56 -0400
Subject: [PATCH 1/3] gh-146075: Prevent crash from malformed `str` subclass

In `partial_vectorcall`, an error returned by `PyDict_Contains` was
considered to be a truthy value. Now, the error is handled
appropriately.
---
 Lib/test/test_functools.py | 12 ++++++++++++
 Modules/_functoolsmodule.c |  6 +++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index dda42cb33072c3..efa85b564f7cdf 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -565,7 +565,19 @@ def __repr__(self):
         g_partial = functools.partial(func, trigger, None, None, None, None, arg=None)
         self.assertEqual(repr(g_partial),"functools.partial(Function(old_function), EvilObject, None, None, None, None, arg=None)")
 
+    def test_str_subclass_error(self):
+        class BadStr(str):
+            def __eq__(self, other):
+                raise RuntimeError
+            def __hash__(self):
+                return str.__hash__(self)
+
+        def f(**kwargs):
+            return kwargs
 
+        p = functools.partial(f, poison="")
+        with self.assertRaises(RuntimeError):
+            result = p(**{BadStr("poison"): "new_value"})
 
 @unittest.skipUnless(c_functools, 'requires the C _functools module')
 class TestPartialC(TestPartial, unittest.TestCase):
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index 723080ede1d9ae..576494e846ca0c 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -457,7 +457,11 @@ partial_vectorcall(PyObject *self, PyObject *const *args,
         for (Py_ssize_t i = 0; i < nkwds; ++i) {
             key = PyTuple_GET_ITEM(kwnames, i);
             val = args[nargs + i];
-            if (PyDict_Contains(pto->kw, key)) {
+            int contains = PyDict_Contains(pto->kw, key);
+            if (contains < 0) {
+                goto error;
+            }
+            else if (contains == 1) {
                 if (pto_kw_merged == NULL) {
                     pto_kw_merged = PyDict_Copy(pto->kw);
                     if (pto_kw_merged == NULL) {

From 32c3e01a74069d3a722b55f3358e789fa11c8190 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Tue, 17 Mar 2026 19:30:47 +0000
Subject: [PATCH 2/3] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst  | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst

diff --git a/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst b/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst
new file mode 100644
index 00000000000000..b62ec4f26fef41
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst
@@ -0,0 +1 @@
+Errors when calling :func:`partial` with a malformed keyword will no longer crash the interpreter.

From f1274c7b3acbdff3f65802053ac4aa79885de100 Mon Sep 17 00:00:00 2001
From: bkap123 <97006829+bkap123@users.noreply.github.com>
Date: Tue, 17 Mar 2026 16:01:54 -0400
Subject: [PATCH 3/3] Update 2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst

---
 .../next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst b/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst
index b62ec4f26fef41..792ea3ad668690 100644
--- a/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst
+++ b/Misc/NEWS.d/next/Library/2026-03-17-19-30-45.gh-issue-146075.85sCSh.rst
@@ -1 +1 @@
-Errors when calling :func:`partial` with a malformed keyword will no longer crash the interpreter.
+Errors when calling :func:`functools.partial` with a malformed keyword will no longer crash the interpreter.