# CVE-2026-23143: virtio_net: Fix misalignment bug in struct virtnet_info

> A misalignment bug in the Linux kernel's virtio_net driver can lead to memory corruption, potentially allowing code execution or 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:** 14 Feb 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-23143, DEBIAN-CVE-2026-23143, GHSA-372h-fwqg-rp6x, UBUNTU-CVE-2026-23143

## What is CVE-2026-23143?

CVE-2026-23143 is a medium-severity memory corruption vulnerability in Linux kernel, published on 14 Feb 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:

virtio_net: Fix misalignment bug in struct virtnet_info

Use the new TRAILING_OVERLAP() helper to fix a misalignment bug
along with the following warning:

drivers/net/virtio_net.c:429:46: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM)
and a set of members that would otherwise follow it (in this case
`u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];`). This
overlays the trailing members (rss_hash_key_data) onto the FAM
(hash_key_data) while keeping the FAM and the start of MEMBERS aligned.
The static_assert() ensures this alignment remains.

Notice that due to tail padding in flexible `struct
virtio_net_rss_config_trailer`, `rss_trailer.hash_key_data`
(at offset 83 in struct virtnet_info) and `rss_hash_key_data` (at
offset 84 in struct virtnet_info) are misaligned by one byte. See
below:

struct virtio_net_rss_config_trailer {
        __le16                     max_tx_vq;            /*     0     2 */
        __u8                       hash_key_length;      /*     2     1 */
        __u8                       hash_key_data[];      /*     3     0 */

        /* size: 4, cachelines: 1, members: 3 */
        /* padding: 1 */
        /* last cacheline: 4 bytes */
};

struct virtnet_info {
...
        struct virtio_net_rss_config_trailer rss_trailer; /*    80     4 */

        /* XXX last struct has 1 byte of padding */

        u8                         rss_hash_key_data[40]; /*    84    40 */
...
        /* size: 832, cachelines: 13, members: 48 */
        /* sum members: 801, holes: 8, sum holes: 31 */
        /* paddings: 2, sum paddings: 5 */
};

After changes, those members are correctly aligned at offset 795:

struct virtnet_info {
...
        union {
                struct virtio_net_rss_config_trailer rss_trailer; /*   792     4 */
                struct {
                        unsigned char __offset_to_hash_key_data[3]; /*   792     3 */
                        u8         rss_hash_key_data[40]; /*   795    40 */
                };                                       /*   792    43 */
        };                                               /*   792    44 */
...
        /* size: 840, cachelines: 14, members: 47 */
        /* sum members: 801, holes: 8, sum holes: 35 */
        /* padding: 4 */
        /* paddings: 1, sum paddings: 4 */
        /* last cacheline: 8 bytes */
};

As a result, the RSS key passed to the device is shifted by 1
byte: the last byte is cut off, and instead a (possibly
uninitialized) byte is added at the beginning.

As a last note `struct virtio_net_rss_config_hdr *rss_hdr;` is also
moved to the end, since it seems those three members should stick
around together. :)

## Which versions are affected by CVE-2026-23143?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23143?

Apply the vendor's patch.

## Is CVE-2026-23143 being exploited?

There is no known exploitation of CVE-2026-23143 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-2026-23143 and fix it if it is affected.

What it is: CVE-2026-23143 is a medium-severity memory corruption vulnerability in Linux kernel, published on 14 Feb 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-2026-23143 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-2026-23143/ (Markdown: https://insights.sbomify.com/CVE-2026-23143/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23143
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23143
- OSV: https://osv.dev/vulnerability/CVE-2026-23143

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23143/
Summaries are generated and may contain mistakes; the official description above is the record.