# CVE-2026-46243: smb: client: reject userspace cifs.spnego descriptions

> A local attacker can exploit improper validation of CIFS SPNEGO key descriptions to escalate privileges within the Linux kernel.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **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 Jun 2026
- **Updated:** 15 Oct 2026
- **Also known as:** ALSA-2026:23258, ALSA-2026:23259, AZL-89309, BELL-CVE-2026-46243, DEBIAN-CVE-2026-46243, GHSA-3mg7-pfmq-9qfv, RHSA-2026:23258, RHSA-2026:23259, RHSA-2026:23395, RLSA-2026:23258, RLSA-2026:23259, ROOT-OS-UBUNTU-2204-CVE-2026-46243, ROOT-OS-UBUNTU-2404-CVE-2026-46243, UBUNTU-CVE-2026-46243

## What is CVE-2026-46243?

CVE-2026-46243 is a high-severity vulnerability in Linux kernel, published on 1 Jun 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: reject userspace cifs.spnego descriptions

cifs.spnego key descriptions contain authority-bearing fields such as
pid, uid, creduid, and upcall_target that cifs.upcall treats as
kernel-originating inputs. However, userspace can also create keys of
this type through request_key(2) or add_key(2), allowing those fields to
be supplied without CIFS origin.

Only accept cifs.spnego descriptions while CIFS is using its private
spnego_cred to request the key.

Weakness: CWE-825 (Expired Pointer Dereference), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2026-46243?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `bpftool` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-abi-stablelists` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-core` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-cross-headers` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-debug` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-debug-core` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-debug-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-debug-modules` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-debug-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-doc` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-headers` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-modules` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-rt` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-core` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-debug` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-debug-core` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-debug-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-debug-modules` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-debug-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-modules` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-rt-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.rt7.470.el8_10 |
| `kernel-tools` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-tools-libs` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-tools-libs-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-zfcpdump` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-zfcpdump-core` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-zfcpdump-devel` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-zfcpdump-modules` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `kernel-zfcpdump-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `perf` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `python3-perf` | AlmaLinux:8 | All versions | 4.18.0-553.129.1.el8_10 |
| `bpftool` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.129.1.el8_10 |
| `bpftool-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.129.1.el8_10 |
| `kernel` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.129.1.el8_10 |
| `kernel-abi-stablelists` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.129.1.el8_10 |
| `kernel-core` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.129.1.el8_10 |

Products: Linux kernel.

## How do I fix CVE-2026-46243?

Apply the vendor's patch.

## Is CVE-2026-46243 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46243 exists.

Public exploit code:

- Script para comprobar si la vulnerabilidad de Linux CIFSwitch (CVE-2026-46243) nos afecta. Detecta configuraciones potencialmente vulnerables y mitigaciones sin ejecutar exploits. (github_poc): https://github.com/MrForkBomb/CIFSwitch-Checker-CVE-2026-46243
- Tracking CIFSwitch (CVE-2026-46243), the CIFS cifs.spnego key-origin privilege escalation (github_poc): https://github.com/suominen/cifswitch
- A Go implementation of CIFSwitch (CVE-2026-46243) (github_poc): https://github.com/Koshmare-Blossom/CIFSwitch-go
- Detection script for CIFSwitch - CVE-2026-46243 (github_poc): https://github.com/liamromanis101/cifswitch-check
- CVE-2026-46243 (github_poc): https://github.com/0xredash/CVE-2026-46243

## 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-2026-46243 and fix it if it is affected.

What it is: CVE-2026-46243 is a high-severity vulnerability in Linux kernel, published on 1 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46243 exists.

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-2026-46243/ (Markdown: https://insights.sbomify.com/CVE-2026-46243/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-46243
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-46243
- OSV: https://osv.dev/vulnerability/CVE-2026-46243

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-46243/
Summaries are generated and may contain mistakes; the official description above is the record.