CVEvulnerability
CVE-2026-52940
5.5 MEDIUM
Official page ↗
- Status
- Analyzed
- Published
- 2026-06-24
- Last modified
- 2026-07-08
- Assigner
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
- CVSS 3.1 ([email protected])
- 5.5 MEDIUM — CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Description
In the Linux kernel, the following vulnerability has been resolved:
tun: zero the whole vnet header in tun_put_user()
tun_put_user() declares an on-stack struct virtio_net_hdr_v1_hash_tunnel
without zeroing it. For a non-tunnel skb, virtio_net_hdr_tnl_from_skb()
only initializes the first 10 bytes (sizeof(struct virtio_net_hdr)),
leaving bytes 10..23 (num_buffers and the hash/tunnel fields) as stack
garbage.
An unprivileged user can set the vnet header size to 24 with
TUNSETVNETHDRSZ, so __tun_vnet_hdr_put() copies all 24 bytes of the
partially-initialized struct to userspace, leaking 14 bytes of kernel
stack on every read of a non-tunnel packet.
Fix it the same way tun_get_user() already does by zeroing the whole
header right after declaration.
Affected configurations
• linux linux kernel (>= 6.17 < 6.18.36)
• linux linux kernel (>= 6.19 < 7.0.13)
• linux linux kernel 7.1