# CVE-2026-43215: cifs: Fix locking usage for tcon fields

> A race condition in the Linux kernel CIFS module due to incorrect locking can lead to system instability or denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 6 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43215, DEBIAN-CVE-2026-43215, GHSA-qhpw-2qgq-68px, ROOT-OS-DEBIAN-11-CVE-2026-43215, ROOT-OS-DEBIAN-12-CVE-2026-43215, ROOT-OS-UBUNTU-2204-CVE-2026-43215, ROOT-OS-UBUNTU-2404-CVE-2026-43215, UBUNTU-CVE-2026-43215

## What is CVE-2026-43215?

CVE-2026-43215 is a high-severity vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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

cifs: Fix locking usage for tcon fields

We used to use the cifs_tcp_ses_lock to protect a lot of objects
that are not just the server, ses or tcon lists. We later introduced
srv_lock, ses_lock and tc_lock to protect fields within the
corresponding structs. This was done to provide a more granular
protection and avoid unnecessary serialization.

There were still a couple of uses of cifs_tcp_ses_lock to provide
tcon fields. In this patch, I've replaced them with tc_lock.

Weakness: CWE-667 (Improper Locking), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-43215?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43215?

Apply the vendor's patch.

## Is CVE-2026-43215 being exploited?

There is no known exploitation of CVE-2026-43215 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-2026-43215 and fix it if it is affected.

What it is: CVE-2026-43215 is a high-severity vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-43215 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-2026-43215/ (Markdown: https://insights.sbomify.com/CVE-2026-43215/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43215
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43215
- OSV: https://osv.dev/vulnerability/CVE-2026-43215

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43215/
Summaries are generated and may contain mistakes; the official description above is the record.