prevent buffer overflow in get_data (closes #26171)

Misc/NEWS

@@ -10,6 +10,9 @@ Release date: tba
 Core and Builtins
 -----------------
 
+- Issue #26171: Fix possible integer overflow and heap corruption in
+  zipimporter.get_data().
+
 Library
 -------
 

Modules/zipimport.c

@@ -1111,6 +1111,11 @@ get_data(PyObject *archive, PyObject *toc_entry)
     }
     file_offset += l;           /* Start of file data */
 
+    if (data_size > LONG_MAX - 1) {
+        fclose(fp);
+        PyErr_NoMemory();
+        return NULL;
+    }
     bytes_size = compress == 0 ? data_size : data_size + 1;
     if (bytes_size == 0)
         bytes_size++;