The check_mtab function in client/mount.cifs.c in mount.cifs in smbfs in Samba 3.5.10 and earlier does not properly verify that the (1) device name and (2) mountpoint strings are composed of valid characters, which allows local users to cause a denial of service (mtab corruption) via a crafted string. NOTE: this vulnerability exists because of an incorrect fix for CVE-2010-0547.
smbfs in Samba 3.5.8 and earlier attempts to use (1) mount.cifs to append to the /etc/mtab file and (2) umount.cifs to append to the /etc/mtab.tmp file without first checking whether resource limits would interfere, which allows local users to trigger corruption of the /etc/mtab file via a process with a small RLIMIT_FSIZE value, a related issue to CVE-2011-1089.