# CVE-2026-99137: cifs: don't update i_size in cifs_do_truncate without a cached handle


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** BELL-CVE-2026-99137, DEBIAN-CVE-2026-99137, GHSA-4m2c-p8vw-33gr, UBUNTU-CVE-2026-99137

## What is CVE-2026-99137?

CVE-2026-99137 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

cifs: don't update i_size in cifs_do_truncate without a cached handle

If find_writable_file() returns null, cifs_file_flush will return
0 without issuing set_file_size, and the outer 'if (!rc)' block
will set i_size to 0 before telling the server to truncate.  If
the cifs_open() then fails, the inode will have size 0, while
the server file is unchanged.

Move the netfs_resize_file() and cifs_setsize() into the 'if
(cfile)', so they only run after a successful set_file_size.

In the no-handle else branch, evict stale pages with
truncate_inode_pages before the O_TRUNC open to dispose of old
cache pages, and let the open response set the i_size.

## Which versions are affected by CVE-2026-99137?


## How do I fix CVE-2026-99137?

Upgrade to a fixed version.

## Is CVE-2026-99137 being exploited?

There is no known exploitation of CVE-2026-99137 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99137 and fix it if it is affected.

What it is: CVE-2026-99137 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99137 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-2026-99137/ (Markdown: https://insights.sbomify.com/CVE-2026-99137/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99137
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99137
- OSV: https://osv.dev/vulnerability/CVE-2026-99137

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99137/
Summaries are generated and may contain mistakes; the official description above is the record.