Dear Maintainer, * using an application built with libcurl on Debian 10 (buster) all packages up-to-date an application crash occurs with a stack similar to this:Thread 228 (Thread 0x7fa5d4710700 (LWP 14855)): #5 0x00007fa683151cc1 in Curl_add_handle_to_pipeline (handle=handle@entry=0x7fa650023b70, conn=0x7fa65002f500) at pipeline.c:113 #6 0x00007fa68313630c in multi_runsingle (multi=multi@entry=0x7fa650029760, now=..., data=data@entry=0x7fa650023b70) at multi.c:1479 #7 0x00007fa683136bd9 in curl_multi_perform (multi=multi@entry=0x7fa650029760, running_handles=running_handles@entry=0x7fa5d470f9a4) at multi.c:2218 #8 0x00007fa68312d742 in easy_transfer (multi=0x7fa650029760) at easy.c:686 #9 easy_perform (events=false, data=0x7fa650023b70) at easy.c:780 #10 curl_easy_perform (data=0x7fa650023b70) at easy.c:799 This stack-trace is very similar to the one reported already to curl (https://curl.se/mail/lib-2019-03/0064.html) and fixed in release 7.64.1: https://curl.haxx.se/bug/?i=3686 can you please back-port the required patches to the Debian 10 stable package ?