In the Linux kernel, the following vulnerability has been resolved:
net/packet: fix TOCTOU race on mmap'd vnet_hdr in tpacket_snd()
In tpacket_snd(), when PACKET_VNET_HDR is enabled, vnet_hdr points
directly into the mmap'd TX ring buffer shared with userspace. The
kernel validates the header via __packet_snd_vnet_parse() but then
re-reads all fields later in virtio_net_hdr_to_skb(). A concurrent
userspace thread can modify the vnet_hdr fields between validation
and use, bypassing all safety checks.
The non-TPACKET path (packet_snd()) already correctly copies vnet_hdr
to a stack-local variable. All other vnet_hdr consumers in the kernel
(tun.c, tap.c, virtio_net.c) also use stack copies. The TPACKET TX
path is the only caller of virtio_net_hdr_to_skb() that reads directly
from user-controlled shared memory.
Fix this by copying vnet_hdr from the mmap'd ring buffer to a
stack-local variable before validation and use, consistent with the
approach used in packet_snd() and all other callers.
References
Configurations
Configuration 1 (hide)
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History
19 Oct 2026, 20:17
| Type | Values Removed | Values Added |
|---|---|---|
| CWE | CWE-367 |
15 Oct 2026, 02:19
| Type | Values Removed | Values Added |
|---|---|---|
| References |
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Information
Published : 2026-05-01 14:16
Updated : 2026-10-19 20:17
NVD link : CVE-2026-31700
Mitre link : CVE-2026-31700
CVE.ORG link : CVE-2026-31700
JSON object : View
Products Affected
linux
- linux_kernel