root@c6b200207f1a:/stunnel-5.76# stunnel          
free(): invalid pointer
Aborted (core dumped)

This is my configuration:

engine = pkcs11
engineCtrl = MODULE_PATH:/usr/lib/libeToken.so
engineCtrl = PIN:pin
output = /var/log/stunnel.log
debug=debug

[in-hdt]
client=no
accept = 172.18.1.2:443
connect=127.0.0.1:8080
cert = /etc/stunnel/certs/hdt.pem
key = /etc/stunnel/certs/hdt.key
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

[in-vpc]
client=no
accept = 172.18.2.2:443
connect=127.0.0.1:8081
cert = /etc/stunnel/certs/vpc.pem
key = /etc/stunnel/certs/vpc.key
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

[in-iam]
client=no
accept = 172.18.3.2:443
connect=127.0.0.1:8082
cert = /etc/stunnel/certs/iam.pem
key = /etc/stunnel/certs/iam.key
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

[out-hdt]
client=yes
accept=8080
connect=ip1:443
engineId=pkcs11
sni = hdt
cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert
key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

[out-vpc]
client=yes
accept=8081
connect=ip2:443
engineId=pkcs11
sni = vpc
cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert
key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

[out-iam]
client=yes
accept=8082
connect=ip3:443
engineId=pkcs11
sni = iam
cert=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=cert
key=pkcs11:model=ID%20Prime%20MD;manufacturer=Gemalto;serial=...;token=eToken;id=...;object=...;type=private;pin-value=pin
sessionResume = no
options = NO_TICKET
retry=yes
TIMEOUTclose = 0
debug=debug

When I try run in gdb:

root@c6b200207f1a:/stunnel-5.76# gdb stunnel
GNU gdb (Ubuntu 12.1-0ubuntu1~22.04.2) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from stunnel...
(gdb) r
Starting program: /usr/local/bin/stunnel
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff789f640 (LWP 4875)]
[Thread 0x7ffff789f640 (LWP 4875) exited]
[New Thread 0x7ffff789f640 (LWP 4876)]
[New Thread 0x7ffff6c78640 (LWP 4878)]
free(): invalid pointer

Thread 1 "stunnel" received signal SIGABRT, Aborted.
__pthread_kill_implementation (no_tid=0, signo=6, threadid=140737346406208) at ./nptl/pthread_kill.c:44
44 ./nptl/pthread_kill.c: No such file or directory.
(gdb)

stunnel is running in docker container ubuntu:22.04

Can someone tell where is the problem?

Regards

BS