gh-111841: Fix os.putenv() and os.unsetenv() with embedded NUL on Windows (GH-111842)

1 files changed, 6 insertions, 1 deletions

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 73b80e4..d99b533 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -12280,7 +12280,6 @@ win32_putenv(PyObject *name, PyObject *value)
     }
 
     Py_ssize_t size;
-    /* PyUnicode_AsWideCharString() rejects embedded null characters */
     wchar_t *env = PyUnicode_AsWideCharString(unicode, &size);
     Py_DECREF(unicode);
 
@@ -12294,6 +12293,12 @@ win32_putenv(PyObject *name, PyObject *value)
         PyMem_Free(env);
         return NULL;
     }
+    if (wcslen(env) != (size_t)size) {
+        PyErr_SetString(PyExc_ValueError,
+                        "embedded null character");
+        PyMem_Free(env);
+        return NULL;
+    }
 
     /* _wputenv() and SetEnvironmentVariableW() update the environment in the
        Process Environment Block (PEB). _wputenv() also updates CRT 'environ'