CVE-2026-99115

ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION

Published Oct 28, 2026 CVSS 3.1 · 4.3 Medium EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION

smb2_get_info_filesystem() reports 56 bytes for FS_POSIX_INFORMATION,
that is the whole of FILE_SYSTEM_POSIX_INFO, but never assigns
FileSysIdentifier. Those eight bytes go to the client as they are found
in the response buffer.

The buffer is zeroed on allocation, so a standalone request leaks
nothing. A compound request can leak: the offset of the next response
is advanced by the length pinned for the previous one, so a reply that
was written into the buffer and then dropped in favour of the short
error response of smb2_set_err_rsp() stays there, and the next reply is
laid over it with only the header cleared.

Report the file system id statfs() returned, which is what the field is
for. FileSysIdentifier is __le64 and f_fsid is a pair of ints, so
assemble the value first, val[0] as the low half, and convert it on the
way out.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4904-1 linux-6.12 security update
History
Type Values Removed Values Added
Weaknesses CWE-908
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Linux linux
Vendors & Products Linux linux
Type Values Removed Values Added
Weaknesses CWE-200
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION smb2_get_info_filesystem() reports 56 bytes for FS_POSIX_INFORMATION, that is the whole of FILE_SYSTEM_POSIX_INFO, but never assigns FileSysIdentifier. Those eight bytes go to the client as they are found in the response buffer. The buffer is zeroed on allocation, so a standalone request leaks nothing. A compound request can leak: the offset of the next response is advanced by the length pinned for the previous one, so a reply that was written into the buffer and then dropped in favour of the short error response of smb2_set_err_rsp() stays there, and the next reply is laid over it with only the header cleared. Report the file system id statfs() returned, which is what the field is for. FileSysIdentifier is __le64 and f_fsid is a pair of ints, so assemble the value first, val[0] as the low half, and convert it on the way out.
Title ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 30, 2026, 12:41 PM
Reserved
Sep 25, 2026, 10:25 AM
Status
Received
Published
Oct 28, 2026, 11:17 AM
Modified
Oct 30, 2026, 1:21 PM
Severity
Moderate
Public date
Oct 28, 2026, 12:00 AM