This is behavior introduced in OpenSSH 3.9 (grep for "re-exec" in the release notes https://www.openssh.com/txt/release-3.9 https://www.openssh.com/txt/release-

This is behavior introduced in OpenSSH 3.9 (grep for "re-exec" in the release notes https://www.openssh.com/txt/release-3.9 https://www.openssh.com/txt/release-3.9) You should also be able to see the error message "sshd re-exec requires execution with an absolute path" in the source. If you follow the `rexec_flag` tested above this message, you can see where it calls execv, later in the code.