# CVE-2026-43350: smb: client: require a full NFS mode SID before reading mode bits

> A malicious SMB server can trigger an out-of-bounds read in the Linux kernel SMB client, potentially leaking memory or causing a crash.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/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:** 8 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43350, DEBIAN-CVE-2026-43350, GHSA-xvvm-359f-6vgc, ROOT-OS-DEBIAN-11-CVE-2026-43350, ROOT-OS-DEBIAN-12-CVE-2026-43350, ROOT-OS-UBUNTU-2204-CVE-2026-43350, ROOT-OS-UBUNTU-2404-CVE-2026-43350, UBUNTU-CVE-2026-43350

## What is CVE-2026-43350?

CVE-2026-43350 is a high-severity memory corruption vulnerability in Linux kernel, published on 8 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:

smb: client: require a full NFS mode SID before reading mode bits

parse_dacl() treats an ACE SID matching sid_unix_NFS_mode as an NFS
mode SID and reads sid.sub_auth[2] to recover the mode bits.

That assumes the ACE carries three subauthorities, but compare_sids()
only compares min(a, b) subauthorities.  A malicious server can return
an ACE with num_subauth = 2 and sub_auth[] = {88, 3}, which still
matches sid_unix_NFS_mode and then drives the sub_auth[2] read four
bytes past the end of the ACE.

Require num_subauth >= 3 before treating the ACE as an NFS mode SID.
This keeps the fix local to the special-SID mode path without changing
compare_sids() semantics for the rest of cifsacl.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-43350?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43350?

Apply the vendor's patch.

## Is CVE-2026-43350 being exploited?

There is no known exploitation of CVE-2026-43350 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-2026-43350 and fix it if it is affected.

What it is: CVE-2026-43350 is a high-severity memory corruption vulnerability in Linux kernel, published on 8 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-2026-43350 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-2026-43350/ (Markdown: https://insights.sbomify.com/CVE-2026-43350/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43350
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43350
- OSV: https://osv.dev/vulnerability/CVE-2026-43350

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43350/
Summaries are generated and may contain mistakes; the official description above is the record.