Title: FreeBSD UFS Uncleared Block Data Recovery Vulnerability
Severity: MODERATE
Description:
FreeBSD is an Open Source, freely available operating system maintained by the FreeBSD Project. FreeBSD is designed to offer a flexible, scalable BSD UNIX Operating System with enhancements for the x86 platform.
A problem with the algorithm used to zero blocks and reallocate them may result in a data consistency race condition, leading to an information gathering attack, or potentially elevated privileges. The UNIX File System (UFS) as well as the Second Extended Filesystem (EXT2) implementations used with the FreeBSD operating system are affected by this vulnerability.
Upon freeing blocks of the file system, the blocks enter the bottom of a list of other blocks within the filesystem that are available for use. The kernel zeroes these blocks prior them reaching the front of the list, and being reallocated to the storage of other files.
Under some circumstances, these blocks holding previous files were being allocated prior to being zeroed. Because of this, it is possible to get blocks from the list, and read the contents of files previous deleted.
Affected Products:
- FreeBSD FreeBSD 3.5.1
- FreeBSD FreeBSD 4.2.0
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