A flaw was found in the way stunnel, a socket wrapper which can provide SSL support to ordinary applications, performed (re)initialization of PRNG after fork. When accepting a new connection, the server forks and the child process handles the request. The RAND_bytes() function of openssl doesn't reset its state after the fork, but seeds the PRNG with the output of time(NULL). The most important consequence is that servers using EC (ECDSA) or DSA certificates may under certain conditions leak their private key.
Created attachment 870826 [details] proposed patch
stunnel and rhel7 have the same stunnel version 4.56 so would require fixing in rhel7 atleast if stunnel in fedora is fixed. Still looking into other rhel6/5 branches.
Was going through the code in stunnel 4.56 version and the code uses pthread model and USE_FORK is not used when pthread is detected in rhel and fedora.
(In reply to Avesh Agarwal from comment #4) > Was going through the code in stunnel 4.56 version and the code uses pthread > model and USE_FORK is not used when pthread is detected in rhel and fedora. The same seems true for stunnel versions in rhel6 and rhel5.
As mentioned in the previous comments, this flaw does not affect the version of stunnel shipped with Red Hat Enterprise Linux 5 and 6, since these versions use POSIX threads (pthreads) and no not use fork(). For the same reason this version does not affect the version of stunnel as shipped with Fedora 19 and Fedora 20.
Statement: Not vulnerable. This issue does not affect the version of stunnel package as shipped with Red Hat Enterprise Linux 5 and 6.