Multiple denial-of-service attacks that can be triggered by writing to the terminal exist in PuTTY versions before 0.71.

In PuTTY versions before 0.71 on Windows, local attackers could hijack the application by putting a malicious help file in the same directory as the executable.

A remotely triggerable memory overwrite in RSA key exchange in PuTTY before 0.71 can occur before host key verification.

The TFTP server in ExtraPuTTY 0.30 and earlier allows remote attackers to cause a denial of service (crash) via a large (1) read or (2) write TFTP protocol message.

The ssh_agent_channel_data function in PuTTY before 0.68 allows remote attackers to have unspecified impact via a large length value in an agent protocol message and leveraging the ability to connect to the Unix-domain socket representing the forwarded agent connection, which trigger a buffer overflow.

Multiple untrusted search path vulnerabilities in Putty beta 0.67 allow local users to execute arbitrary code and conduct DLL hijacking attacks via a Trojan horse (1) UxTheme.dll or (2) ntmarta.dll file in the current working directory.

The (1) ssh2_load_userkey and (2) ssh2_save_userkey functions in PuTTY 0.51 through 0.63 do not properly wipe SSH-2 private keys from memory, which allows local users to obtain sensitive information by reading the memory.

PuTTY 0.59 through 0.61 does not clear sensitive process memory when managing user replies that occur during keyboard-interactive authentication, which might allow local users to read login passwords by obtaining access to the process' memory.

Integer overflow in PuTTY 0.62 and earlier, WinSCP before 5.1.6, and other products that use PuTTY allows remote SSH servers to cause a denial of service (crash) and possibly execute arbitrary code in certain applications that use PuTTY via a negative size value in an RSA key signature during the SSH handshake, which triggers a heap-based buffer overflow.

Heap-based buffer underflow in the modmul function in sshbn.c in PuTTY before 0.63 allows remote SSH servers to cause a denial of service (crash) and possibly trigger memory corruption or code execution via a crafted DSA signature, which is not properly handled when performing certain bit-shifting operations during modular multiplication.