diff --git a/Lib/ast.py b/Lib/ast.py
index f445b32040e5fb..42f4dc04804d06 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -59,17 +59,25 @@ def literal_eval(node_or_string):
     """
     if isinstance(node_or_string, str):
         node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval').body
+        return _convert_literal(node_or_string, True)
     elif isinstance(node_or_string, Expression):
         node_or_string = node_or_string.body
     return _convert_literal(node_or_string)
 
 
-def _convert_literal(node):
+_permitted_literal_types = (str, bytes, int, float, complex,
+                            bool, type(None), type(...))
+
+
+def _convert_literal(node, omit_validation=False):
     """
     Used by `literal_eval` to convert an AST node into a value.
     """
     if isinstance(node, Constant):
-        return node.value
+        if omit_validation:
+            return node.value
+        if type(value := node.value) in _permitted_literal_types:
+            return value
     if isinstance(node, Dict) and len(node.keys) == len(node.values):
         return dict(zip(
             map(_convert_literal, node.keys),
@@ -83,9 +91,16 @@ def _convert_literal(node):
         return set(map(_convert_literal, node.elts))
     if (
         isinstance(node, Call) and isinstance(node.func, Name)
-        and node.func.id == 'set' and node.args == node.keywords == []
     ):
-        return set()
+        if node.func.id == 'set' and node.args == node.keywords == []:
+            return set()
+        elif (
+              node.func.id == 'sentinel' and len(node.args) == 1
+              and node.keywords == []
+              and isinstance(arg := node.args[0], Constant)
+              and isinstance(name := arg.value, str)
+        ):
+            return sentinel(name)
     if (
         isinstance(node, UnaryOp)
         and isinstance(node.op, (UAdd, USub))
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 3f8991c79652d3..e3ff105d248021 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -2215,9 +2215,11 @@ def wrap_value(s):
             except NameError:
                 raise ValueError
 
-        if isinstance(value, (str, int, float, bytes, bool, type(None),
-                              sentinel)):
+        if isinstance(value, (str, int, float, bytes, bool, type(None))):
             return ast.Constant(value)
+        elif isinstance(value, sentinel):
+            return ast.Call(func=ast.Name(id='sentinel'),
+                            args=[ast.Constant(value.__name__)])
         raise ValueError
 
     class RewriteSymbolics(ast.NodeTransformer):
diff --git a/Lib/test/test_ast/test_ast.py b/Lib/test/test_ast/test_ast.py
index 7d35fc4ef7c364..f14ac29d15b864 100644
--- a/Lib/test/test_ast/test_ast.py
+++ b/Lib/test/test_ast/test_ast.py
@@ -2032,6 +2032,9 @@ def test_literal_eval(self):
         self.assertEqual(ast.literal_eval('{1, 2, 3}'), {1, 2, 3})
         self.assertEqual(ast.literal_eval('b"hi"'), b"hi")
         self.assertEqual(ast.literal_eval('set()'), set())
+        val = ast.literal_eval('sentinel("xyz")')
+        self.assertTrue(isinstance(val, sentinel))
+        self.assertEqual(val.__name__, "xyz")
         self.assertRaises(ValueError, ast.literal_eval, 'foo()')
         self.assertEqual(ast.literal_eval('6'), 6)
         self.assertEqual(ast.literal_eval('+6'), 6)
@@ -2043,6 +2046,10 @@ def test_literal_eval(self):
         self.assertRaises(ValueError, ast.literal_eval, '++6')
         self.assertRaises(ValueError, ast.literal_eval, '+True')
         self.assertRaises(ValueError, ast.literal_eval, '2+3')
+        # gh-141778: reject values of invalid types
+        node = ast.Expression(body=ast.Constant(object()))
+        ast.fix_missing_locations(node)
+        self.assertRaises(ValueError, ast.literal_eval, node)
 
     def test_literal_eval_str_int_limit(self):
         with support.adjust_int_max_str_digits(4000):
diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
index ff7475447e95a0..3ebaf0128d6bc9 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -6375,7 +6375,9 @@ def test_threading_module_has_signatures(self):
     def test_thread_module_has_signatures(self):
         import _thread
         no_signature = {'RLock'}
-        self._test_module_has_signatures(_thread, no_signature)
+        unsupported_signature = {'interrupt_main'}
+        self._test_module_has_signatures(_thread, no_signature,
+            unsupported_signature=unsupported_signature)
 
     def test_time_module_has_signatures(self):
         no_signature = {
diff --git a/Misc/NEWS.d/next/Library/2025-12-19-07-09-02.gh-issue-141778.VdSWcy.rst b/Misc/NEWS.d/next/Library/2025-12-19-07-09-02.gh-issue-141778.VdSWcy.rst
new file mode 100644
index 00000000000000..77257f65619a06
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-19-07-09-02.gh-issue-141778.VdSWcy.rst
@@ -0,0 +1,2 @@
+Validate value types of :class:`ast.Constant` nodes in the
+:func:`ast.literal_eval`.  Patch by Sergey B Kirpichev.