Exploiting this vulnerability will not be easy: modern memory allocators provide protections against double frees, and the impacted sshd process is unprivileged and heavily sandboxed.

Quick update: we were able to gain arbitrary control of the “rip” register through this bug (i.e., we can jump wherever we want in sshd’s address space) on an unpatched installation of OpenBSD 7.2 (which runs OpenSSH 9.1 by default). This is by no means the end of the story: this was only step 1, bypass the malloc and double-free protections.

source: L