fix(#4326): reject embedded null byte in remote workspace candidate

api/workspace.py

@@ -163,6 +163,8 @@ def _remote_terminal_workspace_candidate(path: str | Path) -> Path | None:
     raw = _strip_surrounding_quotes(str(path)).strip()
     if not raw:
         return None
+    if '\x00' in raw or '\x00' in cwd:
+        return None
     normalized_raw = _normalize_posix_path(raw)
     normalized_cwd = _normalize_posix_path(cwd)
     if normalized_raw is not None and normalized_cwd is not None:

tests/test_remote_terminal_workspace.py

@@ -90,3 +90,23 @@ def test_var_home_workspaces_stay_allowed_before_system_root_blocklist(monkeypat
     monkeypatch.setattr(workspace, "_workspace_access_error", lambda _candidate: None)
 
     assert validator(str(candidate)) == candidate
+
+
+def test_remote_terminal_workspace_rejects_embedded_nullbyte_in_raw_path(monkeypatch):
+    """Embedded null bytes in remote workspace path should be rejected."""
+    monkeypatch.setattr(api_config, "get_config", lambda: _remote_config())
+
+    # Path with embedded null byte
+    nullbyte_path = f"{REMOTE_CWD}/projects\x00/demo"
+
+    assert workspace._remote_terminal_workspace_candidate(nullbyte_path) is None
+
+
+def test_remote_terminal_workspace_rejects_embedded_nullbyte_in_cwd(monkeypatch):
+    """Embedded null bytes in remote terminal cwd should be rejected."""
+    monkeypatch.setattr(api_config, "get_config", lambda: _remote_config(terminal={"backend": "ssh", "cwd": f"{REMOTE_CWD}\x00/malicious"}))
+
+    # Normal path, but remote cwd contains null byte
+    normal_path = f"{REMOTE_CWD}/projects/demo"
+
+    assert workspace._remote_terminal_workspace_candidate(normal_path) is None