Log is overflowed with messages "Possible memory leak at"

Status changed to 'Confirmed' because the bug affects multiple users.

We have same problem, Ubuntu 18.04.4 LTS (stunnel 5.44 on x86_64-pc-linux-gnu platform):

...cut...
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/x509/x_name.c:92: 323949 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/asn1/tasn_new.c:302: 323959 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/bn/bn_lib.c:190: 215980 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/asn1/a_bitstr.c:117: 215980 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/evp/p_lib.c:142: 107992 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../ssl/ssl_sess.c:72: 107986 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../ssl/statem/extensions_clnt.c:1343: 107988 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/rsa/rsa_lib.c:52: 107985 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/asn1/tasn_utl.c:147: 107983 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/asn1/tasn_new.c:97: 107981 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/bn/bn_mont.c:232: 107987 allocations
Jul 22 09:25:42 srv stunnel[14589]: LOG4[107987]: Possible memory leak at ../crypto/stack/stack.c:198: 107975 allocations
Jul 22 09:25:49 srv systemd[1]: Stopping LSB: Start or stop stunnel 4.x (TLS tunnel for network daemons)...
Jul 22 09:25:49 srv stunnel[14576]: INTERNAL ERROR: Bad magic at ssl.c, line 117
Jul 22 09:25:49 srv stunnel4[9157]: Stopping TLS tunnels: ...cut... stopped
...cut...
Jul 22 09:25:49 srv systemd[1]: Starting LSB: Start or stop stunnel 4.x (TLS tunnel for network daemons)...
Jul 22 09:25:50 srv stunnel[9253]: LOG4[ui]: Service [foobar] uses "verifyChain" without subject checks
Jul 22 09:25:50 srv stunnel[9253]: LOG4[ui]: Use "checkHost" or "checkIP" to restrict trusted certificates
Jul 22 09:25:50 srv stunnel4[9197]: Starting TLS tunnels: ...cut... started
Jul 22 09:25:50 srv systemd[1]: Started LSB: Start or stop stunnel 4.x (TLS tunnel for network daemons).
Jul 22 09:25:52 srv stunnel[9216]: LOG2[5]: Double free attempt: ptr=0x7fb72c00c7a0 alloc=client.c:1398 free#1=client.c:1410 free#2=client.c:1410
Jul 22 09:25:54 srv stunnel[9216]: LOG2[11]: Double free attempt: ptr=0x7fb70800c7a0 alloc=client.c:1398 free#1=client.c:1410 free#2=client.c:1410
Jul 22 09:25:54 srv stunnel[9216]: LOG2[14]: Double free attempt: ptr=0x7fb70400c7a0 alloc=client.c:1398 free#1=client.c:1410 free#2=client.c:1410
Jul 22 09:26:00 srv stunnel[9216]: LOG2[17]: Double free attempt: ptr=0x7fb6fc01b1a0 alloc=client.c:1398 free#1=client.c:1410 free#2=client.c:1410
---

And... not only logs, memory is really leaked:
---
## Before restart:
  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14589 root 20 0 2029276 1.460g 5016 S 1.0 75.0 18:14.70 /usr/bin/stunnel4 /etc/stunnel/foobar.conf
## After restart:
  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  580 root 20 0 390604 7084 5556 S 0.0 0.3 0:00.33 /usr/bin/stunnel4 /etc/stunnel/foobar.conf
---

it looks upgrading to 5.58 should fix the memory leak issue, from the release notes:
5.50: Fixed a memory leak in the WIN32 logging subsystem (this one should be unrelated)
5.57: Fixed memory leaks on configuration reloading errors
5.58: Fixed a tiny memory leak in configuration file reload error handling (thx to Richard Könning)

Is it possible to upgrade it to 5.58 on bionic?