CVE-2026-52940 - tun: zero the whole vnet header in tun_put_user()

CVE-2026-52940 - tun: zero the whole vnet header in tun_put_user()

https://cvefeed.io/rssfeed/latest.atom / Wed, 06/24/2026 - 13:01
CVE ID :CVE-2026-52940
Published : June 24, 2026, 7:14 a.m. | 2 hours, 26 minutes ago
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.
Severity: 0.0 | NA
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