said by unibroker:
# ls -l cm-10-20121129-UNOFFICIAL-encore.zip
----rwxr-x system sdcard_rw 157698499 2012-11-28 20:22 cm-10-20121129-UNOFFICIAL-encore.zip
Looks like I have no permissions and Group has them all! Even everyone else has more than me.
I think when you connect over adb you are automatically part of the sdcard_rw group.
If you are looking to flash to this cm rom, your custom bootloader should be able to do it.