From f693ea9d3d6f9352c7d5e8525d7aa7f319bc7359 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Wed, 18 Mar 2026 18:20:35 +0100
Subject: [PATCH] gh-146093: Fix csv _set_str(): check if
 PyUnicode_DecodeASCII() failed (GH-146113)

The function can fail on a memory allocation failure.

Bug reported by devdanzin.
(cherry picked from commit 724c7c8146f44a7c737ec4588a1ee4b9db994f6f)

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Modules/_csv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Modules/_csv.c b/Modules/_csv.c
index aea071cc143328..0b7ff2575fcfec 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -302,8 +302,12 @@ _set_char(const char *name, Py_UCS4 *target, PyObject *src, Py_UCS4 dflt)
 static int
 _set_str(const char *name, PyObject **target, PyObject *src, const char *dflt)
 {
-    if (src == NULL)
+    if (src == NULL) {
         *target = PyUnicode_DecodeASCII(dflt, strlen(dflt), NULL);
+        if (*target == NULL) {
+            return -1;
+        }
+    }
     else {
         if (src == Py_None)
             *target = NULL;