CVE-2015-8872

The set_fat function in fat.c in dosfstools before 4.0 might allow attackers to corrupt a FAT12 filesystem or cause a denial of service (invalid memory read and crash) by writing an odd number of clusters to the third to last entry on a FAT12 filesystem, which triggers an "off-by-two error."

Updated dosfstools package fixes security vulnerabilities:

In dosfstools before 4.0, if the third to last entry was written on a FAT12 filesystem with an odd number of clusters, the second to last entry would be corrupted. This corruption may also lead to invalid memory accesses when the corrupted entry becomes out of bounds and is used later (CVE-2015-8872).

In dosfstools before 4.0, the variable used for storing the FAT size (in bytes) was an unsigned int. Since the size in sectors read from the BPB was not sufficiently checked, this could end up being zero after multiplying it with the sector size while some offsets still stayed excessive. Ultimately it would cause segfaults when accessing FAT entries for which no memory was allocated (CVE-2016-4804).

dosfstools was updated to fix two security issues.

These security issues were fixed:

• CVE-2015-8872: The set_fat function in fat.c in dosfstools might have allowed attackers to corrupt a FAT12 filesystem or cause a denial of service (invalid memory read and crash) by writing an odd number of clusters to the third to last entry on a FAT12 filesystem, which triggers an 'off-by-two error (bsc#980364).
• CVE-2016-4804: The read_boot function in boot.c in dosfstools allowed attackers to cause a denial of service (crash) via a crafted filesystem, which triggers a heap-based buffer overflow in the (1) read_fat function or an out-of-bounds heap read in (2) get_fat function (bsc#980377).

This non-security issue was fixed:

• bsc#912607: Attempt to rename root dir in fsck due to uninitialized fields.

dosfstools was updated to fix two security issues.

These security issues were fixed:

• CVE-2015-8872: The set_fat function in fat.c in dosfstools might have allowed attackers to corrupt a FAT12 filesystem or cause a denial of service (invalid memory read and crash) by writing an odd number of clusters to the third to last entry on a FAT12 filesystem, which triggers an 'off-by-two error (bsc#980364).
• CVE-2016-4804: The read_boot function in boot.c in dosfstools allowed attackers to cause a denial of service (crash) via a crafted filesystem, which triggers a heap-based buffer overflow in the (1) read_fat function or an out-of-bounds heap read in (2) get_fat function (bsc#980377).

Hanno Böck discovered that dosfstools incorrectly handled certain malformed filesystems. A local attacker could use this issue to cause dosfstools to crash, resulting in a denial of service, or possibly execute arbitrary code.