Theodore Y. Ts'o reports:
Fix a potential security vulnerability where an untrusted
filesystem can be corrupted in such a way that a program using
libext2fs will allocate a buffer which is far too small. This
can lead to either a crash or potentially a heap-based buffer
overflow crash. No known exploits exist, but main concern is
where an untrusted user who possesses privileged access in a
guest Xen environment could corrupt a filesystem which is then
accessed by thus allowing the untrusted user to gain privileged
access in the host OS. Thanks to the McAfee AVERT Research group
for reporting this issue.