I have just uploaded the updated Debian package of stunnel 4.53 to the unstable distribution.
As a notable change, beyond the bugfixes and new features in 4.53 itself, this package has enabled the use of compile time 'hardening' options. (See http://wiki.debian.org/Hardening )
Since our build system was already very strict, this did not cause any new warnings or error messages to be output during compile, link or my basic level run time testing. Nevertheles, I wuold kindly request the help of this list in ferreting out any minor issue that may have crept in.
Note that the expected efect of this hardening options is to turn potential vulnerability vectors into hard crashes. Thus, even if a new bug *does* turn out, it's most likely to be an old, hidden, bug.
For the record, the new compile options enabled were
-D_FORTIFY_SOURCE=2 -fPIE -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security
And the new link options
-Wl,-z,relro