CVE-2024-6387

Se encontró una condición de ejecución del controlador de señales en el servidor de OpenSSH (sshd), donde un cliente no se autentica dentro de los segundos de LoginGraceTime (120 de forma predeterminada, 600 en versiones anteriores de OpenSSH), luego se llama al controlador SIGALRM de sshd de forma asincrónica. Sin embargo, este controlador de señales llama a varias funciones que no son seguras para señales asíncronas, por ejemplo, syslog().

A signal handler in sshd(8) calls a function that is not async-signal-safe. The signal handler is invoked when a client does not authenticate within the LoginGraceTime seconds (120 by default). This signal handler executes in the context of the sshd(8)'s privileged code, which is not sandboxed and runs with full root privileges. This issue is a regression of CVE-2006-5051 originally reported by Mark Dowd and accidentally reintroduced in OpenSSH 8.5p1. As a result of calling functions that are not async-signal-safe in the privileged sshd(8) context, a race condition exists that a determined attacker may be able to exploit to allow an unauthenticated remote code execution as root.