---
cve: "CVE-2026-23143"
severity: "LOW"
cvss: 3.1
epss: "11%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-02-14 15:36:08"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-07T20:58:18+02:00"
---

# CVE-2026-23143

> 3.1 LOW

## Beschreibung

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. :)

## Patch verfügbar (OSV)

- Kernel ≥ 6.18.7

## Referenzen

- <https://git.kernel.org/stable/c/ae48108c2310f1dd700e0dbb655c2f1d92ed00fc>
- <https://git.kernel.org/stable/c/4156c3745f06bc197094b9ee97a9584e69ed00bf>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-23143) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_