OpenSSH Server regreSSHion Remote Code Execution

Qualys has discovered a a signal handler race condition vulnerability in OpenSSH's server, sshd. If a client does not authenticate within LoginGraceTime seconds (120 by default, 600 in old OpenSSH versions), then sshd's SIGALRM handler is called asynchronously, but this signal handler calls various functions that are not async-signal-safe - for example, syslog(). This race condition affects sshd in its default configuration.

async authenticate called client code code execution default functions old openssh qualys race race condition regresshion remote code remote code execution safe server signal sshd syslog vulnerability