CVE-2026-46321: tun: free page on short-frame rejection in tun_xdp_one()

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-09 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: tun: free page on short-frame rejection in tun_xdp_one() tun_xdp_one() returns -EINVAL on a frame shorter than ETH_HLEN without freeing the page that vhost_net_build_xdp() allocated for it. tun_sendmsg() discards that -EINVAL and still returns total_len, so vhost_tx_batch() takes the success path and never frees the page; each short frame in a batch leaks one page-frag chunk. A local process that can open /dev/net/tun and /dev/vhost-net can hit this path: it attaches a tun/tap device as the vhost-net backend and feeds TX descriptors whose length minus the virtio-net header is below ETH_HLEN. Each kick leaks the page-frag chunks for that batch, and a tight submission loop exhausts host memory and triggers an OOM panic. Free the page before returning -EINVAL, matching the XDP-program error path in the same function.

Affected products

Linux kernel: from 5.4.281 before 5.5; from 5.10.223 before 5.10.259; from 5.15.164 before 5.15.210; from 6.1.102 before 6.1.176; from 6.6.43 before 6.6.143; from 6.9.12 before 6.10 — fixed in 5.10.259, 5.15.210, 5.5, 6.1.176, 6.10, 6.12.93

How to fix

Upgrade to a fixed version: Linux kernel 5.10.259, 5.15.210, 5.5, 6.1.176. Check the vendor advisory for mitigations.

References

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