gh-140594: Fix an out of bounds read when feeding NUL byte to PyOS_St…

…dioReadline() (GH-140910) (cherry picked from commit 86a0756) Co-authored-by: Shamil <[email protected]> Co-authored-by: Bénédikt Tran <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
python · vstinner · Mar 12, 2026 · Mar 12, 2026 · Mar 12, 2026 · 3fd5283dddd0fa7c7c29d07d413853d9fa555e87
commit 3fd5283dddd0fa7c7c29d07d413853d9fa555e87
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
@@ -195,6 +195,14 @@ def test_run_module_bug1764407(self):
         self.assertTrue(data.find(b'1 loop') != -1)
         self.assertTrue(data.find(b'__main__.Timer') != -1)
 
+    @support.cpython_only
+    def test_null_byte_in_interactive_mode(self):
+        # gh-140594: Fix an out of bounds read when a single NUL character
+        # is read from the standard input in interactive mode.
+        proc = spawn_python('-i')
+        proc.communicate(b'\x00', timeout=support.SHORT_TIMEOUT)
+        self.assertEqual(proc.returncode, 0)
+
     def test_relativedir_bug46421(self):
         # Test `python -m unittest` with a relative directory beginning with ./
         # Note: We have to switch to the project's top module's directory, as per

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-16-23-17.gh-issue-140594.YIWUpl.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-02-16-23-17.gh-issue-140594.YIWUpl.rst
@@ -0,0 +1,2 @@
+Fix an out of bounds read when a single NUL character is read from the standard input.
+Patch by Shamil Abdulaev.
@@ -342,7 +342,7 @@ PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
             break;
         }
         n += strlen(p + n);
-    } while (p[n-1] != '\n');
+    } while (n == 0 || p[n-1] != '\n');
 
     pr = (char *)PyMem_RawRealloc(p, n+1);
     if (pr == NULL) {
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix an out of bounds read when a single NUL character is read from the standard input.
		Patch by Shamil Abdulaev.