diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-07-13-23-59-45.gh-issue-153664.MQYdit.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-13-23-59-45.gh-issue-153664.MQYdit.rst
new file mode 100644
index 00000000000000..db758c4d2c21d2
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-07-13-23-59-45.gh-issue-153664.MQYdit.rst
@@ -0,0 +1,2 @@
+Fix potential use-after-free and reference leaks in cross-interpreter
+``NotShareableError`` error handling.
diff --git a/Python/crossinterp_data_lookup.h b/Python/crossinterp_data_lookup.h
index 54422ad2335cb6..62fe3ff44660b7 100644
--- a/Python/crossinterp_data_lookup.h
+++ b/Python/crossinterp_data_lookup.h
@@ -100,6 +100,7 @@ _PyXI_UnwrapNotShareableError(PyThreadState * tstate, _PyXI_failure *failure)
     if (failure != NULL) {
         _PyXI_errcode code = _PyXI_ERR_NOT_SHAREABLE;
         if (_PyXI_InitFailure(failure, code, exc) < 0) {
+            Py_DECREF(exc);
             return -1;
         }
     }
diff --git a/Python/crossinterp_exceptions.h b/Python/crossinterp_exceptions.h
index 98411adc5eb3f6..0d144ffdaf4f5b 100644
--- a/Python/crossinterp_exceptions.h
+++ b/Python/crossinterp_exceptions.h
@@ -83,6 +83,7 @@ _ensure_notshareableerror(PyThreadState *tstate,
             // A NotShareableError instance is already set.
             assert(cause == NULL);
             _PyErr_SetRaisedException(tstate, ctx);
+            return;
         }
     }
     else {