prevent buffer overflow in get_data (closes #26171)

Misc/NEWS

@@ -36,6 +36,9 @@ Core and Builtins
   __str__, __trunc__, and __float__ returning instances of subclasses of
   str, long, and float to subclasses of str, long, and float correspondingly.
 
+- Issue #26171: Fix possible integer overflow and heap corruption in
+  zipimporter.get_data().
+
 Library
 -------
 

Modules/zipimport.c

@@ -895,6 +895,11 @@ get_data(char *archive, PyObject *toc_entry)
         PyMarshal_ReadShortFromFile(fp);        /* local header size */
     file_offset += l;           /* Start of file data */
 
+    if (data_size > LONG_MAX - 1) {
+        fclose(fp);
+        PyErr_NoMemory();
+        return NULL;
+    }
     raw_data = PyString_FromStringAndSize((char *)NULL, compress == 0 ?
                                           data_size : data_size + 1);
     if (raw_data == NULL) {