CVE-2026-98554

/// Technical description

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

vlan: ensure sufficient headroom in vlan_dev_hard_header()

Callers that only reserve ETH_HLEN or less (such as llc_alloc_frame()),

or skbs allocated before dynamic device/headroom changes (e.g. toggling

VLAN_FLAG_REORDER_HDR or bonding/team switching slaves), can reach

vlan_dev_hard_header() with insufficient headroom and trigger

skb_under_panic().

Use skb_cow_head() in vlan_dev_hard_header() when VLAN_FLAG_REORDER_HDR

is not set to ensure sufficient headroom for the VLAN header(s) and the

underlying device hard header.

Use READ_ONCE() to read dev->hard_header_len and dev->needed_headroom as

they can be updated concurrently under RTNL (e.g. in

vlan_transfer_features()) while vlan_dev_hard_header() runs locklessly on

the transmit path. Also avoid LL_RESERVED_SPACE(dev) here so that the

extra HH_DATA_MOD alignment padding does not trigger unnecessary

pskb_expand_head() reallocations on inner stacked VLAN devices 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