The rsa_verify function in PuTTY before 0.63 (1) does not clear sensitive process memory after use and (2) does not free certain structures containing sensitive process memory, which might allow local users to discover private RSA and DSA keys.
http://www.openwall.com/lists/oss-security/2013/08/06/11
http://www.debian.org/security/2013/dsa-2736
http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/private-key-not-wiped.html
http://secunia.com/advisories/54533
http://secunia.com/advisories/54379
http://lists.opensuse.org/opensuse-updates/2013-08/msg00035.html