The cassandra startup shell script contains this line:
echo Unable to find java executable. Check JAVA_HOME and PATH environment variables. > /dev/stderr
The problem here is the construct "> /dev/stderr". If the user invoking Cassandra has changed user (for example, by SSHing in as a personal user, and then sudo-ing to an application user responsible for executing the Cassandra daemon), then the attempt to open /dev/stderr will fail, because it will point to a PTY node under /dev/pts/ owned by the original user.
Ultimately this leads to the real problem being masked by the confusing error message "bash: /dev/stderr: Permission denied".
The correct technique is to replace "> /dev/stderr" with ">&2" which will write to the already open stderr file descriptor, instead of resolving the chain of symlinks starting at /dev/stderr, and attempting to reopen the target by name.