# CVE-2026-31710: smb: client: fix dir separator in SMB1 UNIX mounts

> Incorrect directory separator handling in SMB1 UNIX mounts may allow path traversal, enabling unauthorized file access or modification.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 21 Sep 2026
- **Also known as:** BELL-CVE-2026-31710, GHSA-8293-64hg-p37m, UBUNTU-CVE-2026-31710

## What is CVE-2026-31710?

CVE-2026-31710 is a medium-severity path traversal vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

smb: client: fix dir separator in SMB1 UNIX mounts

When calling cifs_mount_get_tcon() with SMB1 UNIX mounts,
@cifs_sb->mnt_cifs_flags needs to be read or updated only after
calling reset_cifs_unix_caps(), otherwise it might end up with missing
CIFS_MOUNT_POSIXACL and CIFS_MOUNT_POSIX_PATHS bits.

This fixes the wrong dir separator used in paths caused by the missing
CIFS_MOUNT_POSIX_PATHS bit in cifs_sb_info::mnt_cifs_flags.

## Which versions are affected by CVE-2026-31710?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31710?

Apply the vendor's patch.

## Is CVE-2026-31710 being exploited?

There is no known exploitation of CVE-2026-31710 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31710 and fix it if it is affected.

What it is: CVE-2026-31710 is a medium-severity path traversal vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31710 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31710/ (Markdown: https://insights.sbomify.com/CVE-2026-31710/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31710
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31710
- OSV: https://osv.dev/vulnerability/CVE-2026-31710

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31710/
Summaries are generated and may contain mistakes; the official description above is the record.