CVE 2009-4308
The ext4_decode_error function in fs/ext4/super.c in the ext4 filesystem in the Linux kernel before 2.6.32 allows user-assisted remote attackers to cause a denial of service (NULL pointer dereference), and possibly have unspecified other impact, via a crafted read-only filesystem that lacks a journal.
See the 
CVE page on Mitre.org
for more details.
