# CVE-2026-64121: net: ifb: report ethtool stats over num_tx_queues

> A local attacker can read adjacent kernel memory via ethtool stats on IFB devices with asymmetric queue counts, potentially exposing sensitive data.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** BELL-CVE-2026-64121, DEBIAN-CVE-2026-64121, GHSA-478c-pq6v-xx69, UBUNTU-CVE-2026-64121

## What is CVE-2026-64121?

CVE-2026-64121 is a high-severity vulnerability in Linux kernel, published on 19 Jul 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: ifb: report ethtool stats over num_tx_queues

ifb_dev_init() allocates dp->tx_private to dev->num_tx_queues
entries via kzalloc_objs(*txp, dev->num_tx_queues). Both IFB
per-queue RX and TX stats live in those entries: ifb_xmit() updates
txp->rx_stats using the skb queue mapping, ifb_ri_tasklet() updates
txp->tx_stats, and ifb_stats64() aggregates both over
dev->num_tx_queues.

The ethtool stats callbacks instead size and walk the per-queue
stats with dev->real_num_rx_queues and dev->real_num_tx_queues. With
an asymmetric device where the RX queue count exceeds the TX queue
count, for example:

    ip link add name ifb10 numtxqueues 1 numrxqueues 8 type ifb
    ethtool -S ifb10

ifb_get_ethtool_stats() indexes past the tx_private allocation and
copies adjacent slab data through ETHTOOL_GSTATS.

Use dev->num_tx_queues consistently for the stats strings, the
stats count, and the stats data walks. This reports one RX stats
group and one TX stats group for each backing ifb_q_private entry,
which is the queue set IFB can actually populate.

Reproduced under UML+KASAN at v7.1-rc2:

  BUG: KASAN: slab-out-of-bounds in ifb_fill_stats_data+0x3c/0xae
  Read of size 8 at addr 0000000062dbd228 by task ethtool/36
  ifb_fill_stats_data+0x3c/0xae
  ifb_get_ethtool_stats+0xc0/0x129
  __dev_ethtool+0x1ca5/0x363c
  dev_ethtool+0x123/0x1b3
  dev_ioctl+0x56c/0x744
  sock_do_ioctl+0x15f/0x1b2
  sock_ioctl+0x4d5/0x50a
  sys_ioctl+0xd8b/0xde9

With the patch applied, the same UML+KASAN repro is silent and
ethtool -S ifb10 reports only the stats backed by the single
allocated tx_private entry.

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

## Which versions are affected by CVE-2026-64121?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64121?

Apply the vendor's patch.

## Is CVE-2026-64121 being exploited?

There is no known exploitation of CVE-2026-64121 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-2026-64121 and fix it if it is affected.

What it is: CVE-2026-64121 is a high-severity vulnerability in Linux kernel, published on 19 Jul 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-2026-64121 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-2026-64121/ (Markdown: https://insights.sbomify.com/CVE-2026-64121/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64121
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64121
- OSV: https://osv.dev/vulnerability/CVE-2026-64121

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64121/
Summaries are generated and may contain mistakes; the official description above is the record.