diff '--color=auto' -uNr mailutils-3.21.orig/libmu_sieve/sieve-gram.y mailutils-3.21/libmu_sieve/sieve-gram.y
--- mailutils-3.21.orig/libmu_sieve/sieve-gram.y	2026-07-19 12:44:14.665009953 +0200
+++ mailutils-3.21/libmu_sieve/sieve-gram.y	2026-07-19 12:45:52.637464772 +0200
@@ -34,6 +34,7 @@
 
 static void node_list_add (struct mu_sieve_node_list *list,
 			   struct mu_sieve_node *node);
+static void tree_free (struct mu_sieve_node **tree);
 
 %}
 
@@ -74,6 +75,15 @@ static void node_list_add (struct mu_sieve_node_list *list,
 %type <node> else_part
 %type <node_list> list testlist elsif_branch maybe_elsif

+/* Reclaim partially built syntax trees and identifiers if error recovery
+   discards their semantic values.  Values stored in the machine string and
+   argument pools remain owned by the machine and are released when it is
+   destroyed. */
+%destructor { free ($$); } IDENT
+%destructor { free ($$.ident); } <command>
+%destructor { tree_free (&$$); } <node>
+%destructor { tree_free (&$$.head); } <node_list>
+
 %%

 input        : /* empty */
diff '--color=auto' -uNr mailutils-3.21.orig/libmu_sieve/prog.c mailutils-3.21/libmu_sieve/prog.c
--- mailutils-3.21.orig/libmu_sieve/prog.c	2025-12-28 14:09:52.000000000 +0100
+++ mailutils-3.21/libmu_sieve/prog.c	2026-07-19 13:15:00.000000000 +0200
@@ -316,6 +316,8 @@ mu_i_sv_lint_command (struct mu_sieve_ma
       chk_arg.node = node;
       err = mu_list_foreach (chk_list, _run_checker, &chk_arg);
     }
+
+  mu_list_destroy (&chk_list);
 }  
 
 static void