Bug 2486977 (CVE-2026-46321)

Summary: CVE-2026-46321 kernel: tun: free page on short-frame rejection in tun_xdp_one()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. A local attacker with access to the tun/tap device can exploit this vulnerability. By sending network frames shorter than the expected header length, the system fails to free allocated memory pages, leading to memory leaks. This can exhaust system memory, resulting in a denial of service (DoS) and causing the system to crash.
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Description OSIDB Bzimport 2026-06-09 13:01:15 UTC 
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.
Comment 1 Keith Grant 2026-06-09 17:04:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026060925-CVE-2026-46321-8e46@gregkh/T