CVE-2026-99115 ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99115?
CVE-2026-99115 is a vulnerability in Linux, published on 28 Oct 2026.
Official 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.
Which versions are affected by CVE-2026-99115?
How do I fix CVE-2026-99115?
Upgrade to a fixed version.
Is CVE-2026-99115 being exploited?
There is no known exploitation of CVE-2026-99115 in the wild and no public exploit code.
Sources
Also known as AZL-111212, BELL-CVE-2026-99115, DEBIAN-CVE-2026-99115, GHSA-h75c-7wh7-p5vh, UBUNTU-CVE-2026-99115.