# CVE-2026-23438: net: mvpp2: guard flow control update with global_tx_fc in buffer switching

> A missing NULL check in the Marvell mvpp2 network driver causes a kernel crash when changing MTU on systems without CM3 SRAM, leading to denial of service.

- **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:** 3 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2026-23438, DEBIAN-CVE-2026-23438, GHSA-4m78-cvj8-m5m2, ROOT-OS-DEBIAN-12-CVE-2026-23438, ROOT-OS-DEBIAN-13-CVE-2026-23438, ROOT-OS-UBUNTU-2204-CVE-2026-23438, ROOT-OS-UBUNTU-2404-CVE-2026-23438, UBUNTU-CVE-2026-23438

## What is CVE-2026-23438?

CVE-2026-23438 is a medium-severity vulnerability in Linux kernel, published on 3 Apr 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:

net: mvpp2: guard flow control update with global_tx_fc in buffer switching

mvpp2_bm_switch_buffers() unconditionally calls
mvpp2_bm_pool_update_priv_fc() when switching between per-cpu and
shared buffer pool modes. This function programs CM3 flow control
registers via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference
priv->cm3_base without any NULL check.

When the CM3 SRAM resource is not present in the device tree (the
third reg entry added by commit 60523583b07c ("dts: marvell: add CM3
SRAM memory to cp11x ethernet device tree")), priv->cm3_base remains
NULL and priv->global_tx_fc is false. Any operation that triggers
mvpp2_bm_switch_buffers(), for example an MTU change that crosses
the jumbo frame threshold, will crash:

  Unable to handle kernel NULL pointer dereference at
  virtual address 0000000000000000
  Mem abort info:
    ESR = 0x0000000096000006
    EC = 0x25: DABT (current EL), IL = 32 bits
  pc : readl+0x0/0x18
  lr : mvpp2_cm3_read.isra.0+0x14/0x20
  Call trace:
   readl+0x0/0x18
   mvpp2_bm_pool_update_fc+0x40/0x12c
   mvpp2_bm_pool_update_priv_fc+0x94/0xd8
   mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0
   mvpp2_change_mtu+0x140/0x380
   __dev_set_mtu+0x1c/0x38
   dev_set_mtu_ext+0x78/0x118
   dev_set_mtu+0x48/0xa8
   dev_ifsioc+0x21c/0x43c
   dev_ioctl+0x2d8/0x42c
   sock_ioctl+0x314/0x378

Every other flow control call site in the driver already guards
hardware access with either priv->global_tx_fc or port->tx_fc.
mvpp2_bm_switch_buffers() is the only place that omits this check.

Add the missing priv->global_tx_fc guard to both the disable and
re-enable calls in mvpp2_bm_switch_buffers(), consistent with the
rest of the driver.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23438?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23438?

Apply the vendor's patch.

## Is CVE-2026-23438 being exploited?

There is no known exploitation of CVE-2026-23438 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-2026-23438 and fix it if it is affected.

What it is: CVE-2026-23438 is a medium-severity vulnerability in Linux kernel, published on 3 Apr 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-2026-23438 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-2026-23438/ (Markdown: https://insights.sbomify.com/CVE-2026-23438/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23438
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23438
- OSV: https://osv.dev/vulnerability/CVE-2026-23438

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23438/
Summaries are generated and may contain mistakes; the official description above is the record.