CVE-2026-52940
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.
How to fix
- linux linux_kernel6.18.36, 7.0.13 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| linux linux_kernel | 6.17 ≤ v < 6.18.36, 6.19 ≤ v < 7.0.13, 7.1 | 6.18.36, 7.0.13 |
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