CVE-2026-97965

In the Linux kernel, the following vulnerability has been resolved:

vxlan: initialize _md in vxlan_xmit_one()

If a VXLAN device is configured with both VXLAN_F_COLLECT_METADATA and

VXLAN_F_GBP, and a packet is transmitted through it using an external

ip_tunnel_info that lacks the IP_TUNNEL_VXLAN_OPT_BIT flag, md is left

pointing to the uninitialized _md stack variable:

if (test_bit(IP_TUNNEL_VXLAN_OPT_BIT, info->key.tun_flags)) {

if (info->options_len < sizeof(*md))

goto drop;

md = ip_tunnel_info_opts(info);

}

Because IP_TUNNEL_VXLAN_OPT_BIT is not set, md is not updated and remains

pointing to _md. Later, vxlan_build_skb() is called with md, which

eventually calls vxlan_build_gbp_hdr():

if (vxflags & VXLAN_F_GBP)

vxlan_build_gbp_hdr(vxh, md);

Inside vxlan_build_gbp_hdr(), md->gbp is read:

if (!md->gbp)

return;

gbp = (struct vxlanhdr_gbp *)vxh;

...

if (md->gbp & VXLAN_GBP_DONT_LEARN)

gbp->dont_learn = 1;

If the stack contains garbage, this causes:

1) VXLAN_HF_GBP flag to be spuriously set in the VXLAN header.

2) gbp->dont_learn and gbp->policy_applied to be set from stack bits.

3) gbp->policy_id to receive 16 bits of uninitialized kernel stack data,

leaking it onto the wire.

Fix this by zero-initializing _md. If IP_TUNNEL_VXLAN_OPT_BIT is not

present, md->gbp remains 0, and vxlan_build_gbp_hdr() returns early

without modifying the VXLAN header.