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


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111212, BELL-CVE-2026-99115, DEBIAN-CVE-2026-99115, GHSA-h75c-7wh7-p5vh, UBUNTU-CVE-2026-99115

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99115 and fix it if it is affected.

What it is: CVE-2026-99115 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99115 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-99115/ (Markdown: https://insights.sbomify.com/CVE-2026-99115/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99115
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99115
- OSV: https://osv.dev/vulnerability/CVE-2026-99115

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99115/
Summaries are generated and may contain mistakes; the official description above is the record.