# CVE-2026-99110: smb: client: fix heap overflow in cifs_do_set_acl()


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111200, BELL-CVE-2026-99110, DEBIAN-CVE-2026-99110, GHSA-82wh-j3w4-q4wc, UBUNTU-CVE-2026-99110

## What is CVE-2026-99110?

CVE-2026-99110 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

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

smb: client: fix heap overflow in cifs_do_set_acl()

cifs_set_acl() validates ACL size using posix_acl_xattr_size():

        4 + (count * 8)  // 4-byte header + 8 bytes per ACE

cifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS
wire format into the same buffer:

        6 + (count * 10)  // 6-byte header + 10 bytes per ACE

An ACL that passes the xattr-based check in cifs_set_acl() can
overflow the heap when posix_acl_to_cifs() writes the larger CIFS
format.

Validate the CIFS format size against the remaining buffer space and
USHRT_MAX before converting--data_count is __u16, so sizes above
USHRT_MAX truncate the on-wire packet length, causing the server to
apply a partial ACL.  Replace MaxDataCount = 1000 with
min(CIFSMaxBufSize, USHRT_MAX).

## Which versions are affected by CVE-2026-99110?


## How do I fix CVE-2026-99110?

Upgrade to a fixed version.

## Is CVE-2026-99110 being exploited?

There is no known exploitation of CVE-2026-99110 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99110 and fix it if it is affected.

What it is: CVE-2026-99110 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99110 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-2026-99110/ (Markdown: https://insights.sbomify.com/CVE-2026-99110/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99110
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99110
- OSV: https://osv.dev/vulnerability/CVE-2026-99110

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99110/
Summaries are generated and may contain mistakes; the official description above is the record.