# CVE-2026-99115: ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION

CVE-2026-99115 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-99115, released November 3, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-99115
- Priority: Routine
- CVSS: 3.1 (Low)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 28, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-99115

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.115-2 | [DEBIAN-CVE-2026-99115](https://patchblox.com/security/data/fix/linux/debian-cve-2026-99115.md) | Nov 3, 2026 |
| Linux | linux Debian 14 | 7.2.13-1 | [DEBIAN-CVE-2026-99115](https://patchblox.com/security/data/fix/linux/debian-cve-2026-99115.md) | Nov 3, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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