diff -ru libz-1.2.8.2015.12.26.orig/inflate.c libz-1.2.8.2015.12.26/inflate.c

--- libz-1.2.8.2015.12.26.orig/inflate.c	2015-12-21 23:37:02.000000000 +0100

+++ libz-1.2.8.2015.12.26/inflate.c	2022-10-27 11:32:39.403516533 +0200

@@ -595,8 +595,9 @@

                 if (copy > have) copy = have;

                 if (copy) {

                     if (state->head != NULL &&

-                        state->head->extra != NULL) {

-                        len = state->head->extra_len - state->length;

+                        state->head->extra != NULL &&

+                        (len = state->head->extra_max - state->length) <

+                            state->head->extra_max) {

                         memcpy(state->head->extra + len, next,

                                len + copy > state->head->extra_max ?

                                state->head->extra_max - len : copy);