ssh-agent is a program to hold private keys used for OpenSSH public key authentication. Connections to ssh-agent may be forwarded from further remote hosts using the -A option to ssh. The server to which the ssh-agent connection is forwarded may cause the ssh-agent process to load (and unload) operating system-provided shared libraries to support the addition and deletion of PKCS#11 keys.The server may cause ssh-agent to load shared libraries other than those required for PKCS#11 support. These shared libraries may have side effects that occur on load and unload (dlopen and dlclose). An attacker with access to a server that accepts a forwarded ssh-agent connection may be able to execute code on the machine running ssh-agent. Note that the attack relies on properties of operating system-provided libraries. This has been demonstrated on other operating systems; it is unknown whether this attack is possible using the libraries provided by a FreeBSD installation.