In the Linux kernel, the following vulnerability has been resolved:
ntfs: fix off-by-one in mapping pairs decoding bounds checks
In ntfs_mapping_pairs_decompress(), attr_end points one byte past the
end of the attribute record:
<pre>
attr_end = (u8 *)attr + le32_to_cpu(attr->length);
</pre>
The two bounds checks validating that mapping pair data bytes fit within
the attribute use strict greater-than (>), which allows a one-byte
out-of-bounds read when the data extends exactly to attr_end:
b = *buf & 0xf;
if (b) {
if (unlikely(buf + b > attr_end)) // off-by-one
goto io_error;
for (deltaxcn = (s8)buf[b--]; b; b--)
deltaxcn = (deltaxcn << 8) + buf[b];
}
When buf + b == attr_end, the check evaluates to false and buf[b] reads
one byte past the valid attribute boundary. The same pattern appears in
the LCN delta bytes check.
Fix both checks to use >= so that buf[b] at exactly attr_end is
correctly rejected as out of bounds.
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS Score: 9.8
AV:N - The legacy NTFS driver is exported via nfsd and commonly shared over ksmbd; remote NFS/SMB reads on an NTFS-backed export reach ntfs_mapping_pairs_decompress() through VFS read/iomap and ntfs_map_runlist() without further local access.
AC:L - An attacker fully controls a crafted NTFS image offline and can place mapping pairs to hit the exact off-by-one boundary, reliably triggering the flaw on mount or on the next access that decompresses that attribute extent.
PR:N - Exploitation needs only the ability to trigger server-side parsing of the mounted volume (e.g., guest/anonymous SMB or permissive NFS export); no init-namespace root or CAP_SYS_ADMIN on the victim is required at trigger time.
UI:N - After an administrator mounts the poisoned volume, a remote client can trigger the bug with protocol read/open operations alone; no additional end-user clicks, plug-in events, or mount actions are needed during exploitation.
S:U - Impact stays within kernel/host context (metadata parsing, runlist corruption, and resulting I/O); it does not cross a VM, container, or IOMMU security boundary to another authority.
C:H - The flawed bounds check permits a one-byte out-of-bounds kernel read past the attribute end, often into MFT record slack that may contain stale cached data, matching OOB-read disclosure impact.
I:H - The leaked byte is folded into runlist length/LCN deltas, yielding attacker-influenced cluster mappings that can misdirect subsequent kernel block I/O and corrupt arbitrary on-volume metadata or file data.
A:H - Corrupt runlists and failed decompression paths surface as ntfs_error/EIO during mount or I/O and can panic or wedge the node under repeated remote access, giving a practical denial-of-service.
| Attack Vector |
Network |
Scope |
Unchanged |
| Attack Complexity |
Low |
Confidentiality Impact |
High |
| Privileges Required |
None |
Integrity Impact |
High |
| User Interaction |
None |
Availability Impact |
High |
AV:N - The legacy NTFS driver is exported via nfsd and commonly shared over ksmbd; remote NFS/SMB reads on an NTFS-backed export reach ntfs_mapping_pairs_decompress() through VFS read/iomap and ntfs_map_runlist() without further local access.
AC:L - An attacker fully controls a crafted NTFS image offline and can place mapping pairs to hit the exact off-by-one boundary, reliably triggering the flaw on mount or on the next access that decompresses that attribute extent.
PR:N - Exploitation needs only the ability to trigger server-side parsing of the mounted volume (e.g., guest/anonymous SMB or permissive NFS export); no init-namespace root or CAP_SYS_ADMIN on the victim is required at trigger time.
UI:N - After an administrator mounts the poisoned volume, a remote client can trigger the bug with protocol read/open operations alone; no additional end-user clicks, plug-in events, or mount actions are needed during exploitation.
S:U - Impact stays within kernel/host context (metadata parsing, runlist corruption, and resulting I/O); it does not cross a VM, container, or IOMMU security boundary to another authority.
C:H - The flawed bounds check permits a one-byte out-of-bounds kernel read past the attribute end, often into MFT record slack that may contain stale cached data, matching OOB-read disclosure impact.
I:H - The leaked byte is folded into runlist length/LCN deltas, yielding attacker-influenced cluster mappings that can misdirect subsequent kernel block I/O and corrupt arbitrary on-volume metadata or file data.
A:H - Corrupt runlists and failed decompression paths surface as ntfs_error/EIO during mount or I/O and can panic or wedge the node under repeated remote access, giving a practical denial-of-service.
CVSS 3.1