CVE-2026-31684

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> net: sched: act_csum: validate nested VLAN headers<br /> <br /> tcf_csum_act() walks nested VLAN headers directly from skb-&gt;data when an<br /> skb still carries in-payload VLAN tags. The current code reads<br /> vlan-&gt;h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without<br /> first ensuring that the full VLAN header is present in the linear area.<br /> <br /> If only part of an inner VLAN header is linearized, accessing<br /> h_vlan_encapsulated_proto reads past the linear area, and the following<br /> skb_pull(VLAN_HLEN) may violate skb invariants.<br /> <br /> Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and<br /> pulling each nested VLAN header. If the header still is not fully<br /> available, drop the packet through the existing error path.