samba -- format string bug in afsacl.so VFS plugin

The Samba Team reports:

NOTE: This security advisory only impacts Samba servers
that share AFS file systems to CIFS clients and which have
been explicitly instructed in smb.conf to load the afsacl.so
VFS module.
The source defect results in the name of a file stored on
disk being used as the format string in a call to snprintf().
This bug becomes exploitable only when a user is able
to write to a share which utilizes Samba’s afsacl.so library
for setting Windows NT access control lists on files residing
on an AFS file system.