Overview:
When using scp -rp to copy a directory with sticky bit on (such as /tmp), the sticky bit is not preserved.

Reproduction:
Create a directory dir with permissions 1777. Then use
scp -rp dir user@otherhost:
The resulting directory on the otherhost will have permissions of 0777 instead of 1777. From the security point of view this may considered a serious problem.

Location of the problem:
in scp.c the FILEMODEMASK does not include the sticky bit (S_ISVTX).