The OCSP functionality in stunnel before 4.24 does not properly search certificate revocation lists (CRL), which allows remote attackers to bypass intended access restrictions by using revoked certificates.
https://www.redhat.com/archives/fedora-package-announce/2008-May/msg00942.html
https://www.redhat.com/archives/fedora-package-announce/2008-May/msg00907.html
https://www.redhat.com/archives/fedora-package-announce/2008-May/msg00856.html
https://exchange.xforce.ibmcloud.com/vulnerabilities/42528
http://www.vupen.com/english/advisories/2008/1569/references
http://www.securityfocus.com/bid/29309
http://www.mandriva.com/security/advisories?name=MDVSA-2008:168
http://stunnel.mirt.net/pipermail/stunnel-announce/2008-May/000035.html
http://security.gentoo.org/glsa/glsa-200808-08.xml
http://secunia.com/advisories/31438