Stacktrace:
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
         set = {__val = {0, 140337533684800, 140725801169072, 94865733453904, 140725801169056, 15442105031219824384, 4, 94865733453904, 0, 15442105031219824384, 4, 1, 94865733453904, 1, 4, 94865708102691}}
         pid = <optimized out>
         tid = <optimized out>
         ret = <optimized out>
 #1  0x00007fa2e09d5801 in __GI_abort () at abort.c:79
         save_stage = 1
         act = {__sigaction_handler = {sa_handler = 0x5647a656bd10, sa_sigaction = 0x5647a656bd10}, sa_mask = {__val = {94865708083362, 1572911363, 206158430224, 140725801169664, 94865708014912, 17179869207, 17179869201, 511101108234, 1318554959873, 94862942666752, 18446744073709530016, 94865733327264, 94865707998636, 94865708111963, 140725801169488, 94865708083362}}, sa_flags = -1529528963, sa_restorer = 0x75}
         sigs = {__val = {32, 0 <repeats 15 times>}}
         __cnt = <optimized out>
         __set = <optimized out>
         __cnt = <optimized out>
         __set = <optimized out>
 #2  0x00005647a4d3e3d0 in ?? ()
 No symbol table info available.
 #3  0x00005647a4d395b3 in ?? ()
 No symbol table info available.
 #4  0x00005647a4d39809 in ?? ()
 No symbol table info available.
 #5  0x00005647a4d39e44 in ?? ()
 No symbol table info available.
 #6  0x00007fa2e17ab7c8 in CRYPTO_free_ex_data (class_index=class_index@entry=2, obj=obj@entry=0x7fa2d0019f90, ad=ad@entry=0x7fa2d001a0e0) at ../crypto/ex_data.c:354
         mx = <optimized out>
         i = 2
         ip = 0x7fa2e1aff6f0 <ex_data+16>
         ptr = <optimized out>
         f = 0x5647a656b430
         stack = {0x0, 0x5647a656b3a0, 0x5647a656b430, 0xd64d60b5ca214700, 0x7fa2d000bc80, 0x5647a65715f0, 0x7fa2d0019f90, 0x7fa2e17ab2c8 <CRYPTO_get_ex_data+24>, 0x5, 0x5647a65715f0}
         storage = 0x7ffd4763b370
 #7  0x00007fa2e1b3fe58 in SSL_SESSION_free (ss=0x7fa2d0019f90) at ../ssl/ssl_sess.c:787
         i = <optimized out>
         ss = 0x7fa2d0019f90
         i = <optimized out>
         i = <optimized out>
 #8  0x00007fa2e17af3fc in doall_util_fn (arg=0x7ffd4763b460, arg@entry=0x7ffd4763b420, func_arg=func_arg@entry=0x7fa2e1b406f0 <timeout_cb>, func=0x0, use_arg=1, lh=0x5647a6551d40) at ../crypto/lhash/lhash.c:196
         i = 5
         a = <optimized out>
         n = 0x7fa2c8012800
         i = <optimized out>
         a = <optimized out>
         n = <optimized out>
 #9  OPENSSL_LH_doall_arg (lh=0x5647a6551d40, func=func@entry=0x7fa2e1b406f0 <timeout_cb>, arg=arg@entry=0x7ffd4763b460) at ../crypto/lhash/lhash.c:211
 No locals.
 #10 0x00007fa2e1b414e7 in lh_SSL_SESSION_doall_TIMEOUT_PARAM (arg=0x7ffd4763b460, fn=0x7fa2e1b406f0 <timeout_cb>, lh=<optimized out>) at ../ssl/ssl_sess.c:1104
 No locals.
 #11 SSL_CTX_flush_sessions (s=0x5647a65715f0, t=<optimized out>) at ../ssl/ssl_sess.c:1119
         i = <optimized out>
         tp = {ctx = 0x5647a65715f0, time = 1572911664, cache = 0x5647a6551d40}
 #12 0x00005647a4d4d080 in ?? ()
 No symbol table info available.
 #13 0x00005647a4d4d109 in ?? ()
 No symbol table info available.
 #14 0x00005647a4d38c56 in ?? ()
 No symbol table info available.
 #15 0x00007fa2e09b6b97 in __libc_start_main (main=0x5647a4d38be0, argc=2, argv=0x7ffd4763b688, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd4763b678) at ../csu/libc-start.c:310
         self = <optimized out>
         __self = <optimized out>
         result = <optimized out>
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, -5506946324664727591, 94865707995104, 140725801170560, 0, 0, -2240925574734854183, -2280530182707525671}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x7fa2e1d9e733 <_dl_init+259>, 0x7fa2e1d816b8}, data = {prev = 0x0, cleanup = 0x0, canceltype = -505813197}}}
         not_first_call = <optimized out>
 #16 0x00005647a4d3900a in ?? ()
 No symbol table info available.
StacktraceAddressSignature: /usr/bin/stunnel4:6:/lib/x86_64-linux-gnu/libc-2.27.so+40801:/usr/bin/stunnel4+e3d0:/usr/bin/stunnel4+95b3:/usr/bin/stunnel4+9809:/usr/bin/stunnel4+9e44:/usr/lib/x86_64-linux-gnu/libcrypto.so.1.1+1757c8:/usr/lib/x86_64-linux-gnu/libssl.so.1.1+3ee58:/usr/lib/x86_64-linux-gnu/libcrypto.so.1.1+1793fc:/usr/lib/x86_64-linux-gnu/libssl.so.1.1+404e7:/usr/bin/stunnel4+1d080:/usr/bin/stunnel4+1d109:/usr/bin/stunnel4+8c56:/lib/x86_64-linux-gnu/libc-2.27.so+21b97:/usr/bin/stunnel4+900a
StacktraceSource:
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
   [Error: raise.c was not found in source tree]
 #1  0x00007fa2e09d5801 in __GI_abort () at abort.c:79
   [Error: abort.c was not found in source tree]
 #2  0x00005647a4d3e3d0 in ?? ()
 #3  0x00005647a4d395b3 in ?? ()
 #4  0x00005647a4d39809 in ?? ()
 #5  0x00005647a4d39e44 in ?? ()
 #6  0x00007fa2e17ab7c8 in CRYPTO_free_ex_data (class_index=class_index@entry=2, obj=obj@entry=0x7fa2d0019f90, ad=ad@entry=0x7fa2d001a0e0) at ../crypto/ex_data.c:354
   [Error: ex_data.c was not found in source tree]
 #7  0x00007fa2e1b3fe58 in SSL_SESSION_free (ss=0x7fa2d0019f90) at ../ssl/ssl_sess.c:787
   [Error: ssl_sess.c was not found in source tree]
 #8  0x00007fa2e17af3fc in doall_util_fn (arg=0x7ffd4763b460, arg@entry=0x7ffd4763b420, func_arg=func_arg@entry=0x7fa2e1b406f0 <timeout_cb>, func=0x0, use_arg=1, lh=0x5647a6551d40) at ../crypto/lhash/lhash.c:196
   [Error: lhash.c was not found in source tree]
 #9  OPENSSL_LH_doall_arg (lh=0x5647a6551d40, func=func@entry=0x7fa2e1b406f0 <timeout_cb>, arg=arg@entry=0x7ffd4763b460) at ../crypto/lhash/lhash.c:211
   [Error: lhash.c was not found in source tree]
 #10 0x00007fa2e1b414e7 in lh_SSL_SESSION_doall_TIMEOUT_PARAM (arg=0x7ffd4763b460, fn=0x7fa2e1b406f0 <timeout_cb>, lh=<optimized out>) at ../ssl/ssl_sess.c:1104
   [Error: ssl_sess.c was not found in source tree]
 #11 SSL_CTX_flush_sessions (s=0x5647a65715f0, t=<optimized out>) at ../ssl/ssl_sess.c:1119
   [Error: ssl_sess.c was not found in source tree]
 #12 0x00005647a4d4d080 in ?? ()
 #13 0x00005647a4d4d109 in ?? ()
 #14 0x00005647a4d38c56 in ?? ()
 #15 0x00007fa2e09b6b97 in __libc_start_main (main=0x5647a4d38be0, argc=2, argv=0x7ffd4763b688, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd4763b678) at ../csu/libc-start.c:310
   [Error: libc-start.c was not found in source tree]
 #16 0x00005647a4d3900a in ?? ()

StacktraceTop:
 ?? ()
 ?? ()
 ?? ()
 ?? ()
 CRYPTO_free_ex_data (class_index=class_index@entry=2, obj=obj@entry=0x7fa2d0019f90, ad=ad@entry=0x7fa2d001a0e0) at ../crypto/ex_data.c:354
ThreadStacktrace:
 .
 Thread 2 (Thread 0x7fa2df7ea700 (LWP 24375)):
 #0  0x00007fa2e0a799d0 in __GI___nanosleep (requested_time=requested_time@entry=0x7fa2df7e9df0, remaining=remaining@entry=0x7fa2df7e9df0) at ../sysdeps/unix/sysv/linux/nanosleep.c:28
         resultvar = 18446744073709551100
         sc_cancel_oldtype = 0
         sc_ret = <optimized out>
 #1  0x00007fa2e0a798aa in __sleep (seconds=0) at ../sysdeps/posix/sleep.c:55
         save_errno = 0
         ts = {tv_sec = 12254, tv_nsec = 870006639}
 #2  0x00005647a4d4c64f in ?? ()
 No symbol table info available.
 #3  0x00007fa2e0d8d6db in start_thread (arg=0x7fa2df7ea700) at pthread_create.c:463
         pd = 0x7fa2df7ea700
         now = <optimized out>
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140337511048960, 2241716018176542681, 140337511046976, 0, 0, 140725801169984, -2280631025661425703, -2280530710522279975}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
         not_first_call = <optimized out>
 #4  0x00007fa2e0ab688f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
 No locals.
 .
 Thread 1 (Thread 0x7fa2e1fa80c0 (LWP 24373)):
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
         set = {__val = {0, 140337533684800, 140725801169072, 94865733453904, 140725801169056, 15442105031219824384, 4, 94865733453904, 0, 15442105031219824384, 4, 1, 94865733453904, 1, 4, 94865708102691}}
         pid = <optimized out>
         tid = <optimized out>
         ret = <optimized out>
 #1  0x00007fa2e09d5801 in __GI_abort () at abort.c:79
         save_stage = 1
         act = {__sigaction_handler = {sa_handler = 0x5647a656bd10, sa_sigaction = 0x5647a656bd10}, sa_mask = {__val = {94865708083362, 1572911363, 206158430224, 140725801169664, 94865708014912, 17179869207, 17179869201, 511101108234, 1318554959873, 94862942666752, 18446744073709530016, 94865733327264, 94865707998636, 94865708111963, 140725801169488, 94865708083362}}, sa_flags = -1529528963, sa_restorer = 0x75}
         sigs = {__val = {32, 0 <repeats 15 times>}}
         __cnt = <optimized out>
         __set = <optimized out>
         __cnt = <optimized out>
         __set = <optimized out>
 #2  0x00005647a4d3e3d0 in ?? ()
 No symbol table info available.
 #3  0x00005647a4d395b3 in ?? ()
 No symbol table info available.
 #4  0x00005647a4d39809 in ?? ()
 No symbol table info available.
 #5  0x00005647a4d39e44 in ?? ()
 No symbol table info available.
 #6  0x00007fa2e17ab7c8 in CRYPTO_free_ex_data (class_index=class_index@entry=2, obj=obj@entry=0x7fa2d0019f90, ad=ad@entry=0x7fa2d001a0e0) at ../crypto/ex_data.c:354
         mx = <optimized out>
         i = 2
         ip = 0x7fa2e1aff6f0 <ex_data+16>
         ptr = <optimized out>
         f = 0x5647a656b430
         stack = {0x0, 0x5647a656b3a0, 0x5647a656b430, 0xd64d60b5ca214700, 0x7fa2d000bc80, 0x5647a65715f0, 0x7fa2d0019f90, 0x7fa2e17ab2c8 <CRYPTO_get_ex_data+24>, 0x5, 0x5647a65715f0}
         storage = 0x7ffd4763b370
 #7  0x00007fa2e1b3fe58 in SSL_SESSION_free (ss=0x7fa2d0019f90) at ../ssl/ssl_sess.c:787
         i = <optimized out>
         ss = 0x7fa2d0019f90
         i = <optimized out>
         i = <optimized out>
 #8  0x00007fa2e17af3fc in doall_util_fn (arg=0x7ffd4763b460, arg@entry=0x7ffd4763b420, func_arg=func_arg@entry=0x7fa2e1b406f0 <timeout_cb>, func=0x0, use_arg=1, lh=0x5647a6551d40) at ../crypto/lhash/lhash.c:196
         i = 5
         a = <optimized out>
         n = 0x7fa2c8012800
         i = <optimized out>
         a = <optimized out>
         n = <optimized out>
 #9  OPENSSL_LH_doall_arg (lh=0x5647a6551d40, func=func@entry=0x7fa2e1b406f0 <timeout_cb>, arg=arg@entry=0x7ffd4763b460) at ../crypto/lhash/lhash.c:211
 No locals.
 #10 0x00007fa2e1b414e7 in lh_SSL_SESSION_doall_TIMEOUT_PARAM (arg=0x7ffd4763b460, fn=0x7fa2e1b406f0 <timeout_cb>, lh=<optimized out>) at ../ssl/ssl_sess.c:1104
 No locals.
 #11 SSL_CTX_flush_sessions (s=0x5647a65715f0, t=<optimized out>) at ../ssl/ssl_sess.c:1119
         i = <optimized out>
         tp = {ctx = 0x5647a65715f0, time = 1572911664, cache = 0x5647a6551d40}
 #12 0x00005647a4d4d080 in ?? ()
 No symbol table info available.
 #13 0x00005647a4d4d109 in ?? ()
 No symbol table info available.
 #14 0x00005647a4d38c56 in ?? ()
 No symbol table info available.
 #15 0x00007fa2e09b6b97 in __libc_start_main (main=0x5647a4d38be0, argc=2, argv=0x7ffd4763b688, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffd4763b678) at ../csu/libc-start.c:310
         self = <optimized out>
         __self = <optimized out>
         result = <optimized out>
         unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, -5506946324664727591, 94865707995104, 140725801170560, 0, 0, -2240925574734854183, -2280530182707525671}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x7fa2e1d9e733 <_dl_init+259>, 0x7fa2e1d816b8}, data = {prev = 0x0, cleanup = 0x0, canceltype = -505813197}}}
         not_first_call = <optimized out>
 #16 0x00005647a4d3900a in ?? ()
 No symbol table info available.