PuTTY 0.53b and earlier does not clear logon credentials from memory, including plaintext passwords, which could allow attackers with access to memory to steal the SSH credentials.

schpw.c in the kpasswd service in kadmind in MIT Kerberos 5 (aka krb5) before 1.11.3 does not properly validate UDP packets before sending responses, which allows remote attackers to cause a denial of service (CPU and bandwidth consumption) via a forged packet that triggers a communication loop, as demonstrated by krb_pingpong.nasl, a related issue to CVE-1999-0103.

operator new[] sometimes returns pointers to heap blocks which are too small. When a new array is allocated, the C++ run-time has to calculate its size. The product may exceed the maximum value which can be stored in a machine register. This error is ignored, and the truncated value is used for the heap allocation. This may lead to heap overflows and therefore security bugs. (See http://cert.uni-stuttgart.de/advisories/calloc.php for further references.)

firewalls might let some TCP flags combinations pass (e.g. all with RST flag set) and the OS (e.g. Linux) stack would in turn accept a TCP session it might not have accepted otherwise.