Buffer overflow in sshbn.c in PuTTY before 0.63 allows remote SSH servers to cause a denial of service (crash) via an invalid DSA signature that is not properly handled during computation of a modular inverse and triggers the overflow during a division by zero by the bignum functionality, a different vulnerability than CVE-2013-4206.
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/vuln-bignum-division-by-zero.html
http://secunia.com/advisories/54533
http://secunia.com/advisories/54379
http://lists.opensuse.org/opensuse-updates/2013-08/msg00035.html