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

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 include Linux kernel.

How do I fix CVE-2026-23143?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

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 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-23143, DEBIAN-CVE-2026-23143, GHSA-372h-fwqg-rp6x, UBUNTU-CVE-2026-23143.