On 64-bit systems, the implementation of VOP_VPTOFH() in the cd9660, tarfs and ext2fs filesystems overflows the destination FID buffer by 4 bytes, a stack buffer overflow. A NFS server that exports a cd9660, tarfs, or ext2fs file system can be made to panic by mounting and accessing the export with an NFS client. Further exploitation (e.g., bypassing file permission checking or remote kernel code execution) is potentially possible, though this has not been demonstrated. In particular, release kernels are compiled with stack protection enabled, and some instances of the overflow are caught by this mechanism, causing a panic.
A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).