CVE-2026-98377

/// Technical description

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

vlan: require the MAC header to be present in __vlan_insert_inner_tag()

__vlan_insert_inner_tag() only guarantees head room via skb_cow_head(),

never that mac_len bytes of MAC header are present. Its ETH_HLEN

wrappers - __vlan_insert_tag() under skb_vlan_push(), and

vlan_insert_tag() under validate_xmit_vlan() on the generic transmit

path - therefore rewrite the first 16 bytes at skb->data: a 12-byte

memmove plus two 2-byte stores at +12 and +14. No caller supplies the

bound, while the pop helpers use skb_ensure_writable()/pskb_may_pull().

An IFF_TUN device has hard_header_len == 0, so packet_snd() accepts a

one-byte AF_PACKET/SOCK_RAW frame. The first vlan push only sets a

hwaccel tag; the next - clsact "action vlan push" or

bpf_skb_vlan_push() - enters the helper with skb->len still 1. The

head comes from skbuff_small_head without __GFP_ZERO, so each push

drags bytes from beyond skb->tail into the frame. Afte

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References