Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-10-18T00:00:00 kernel: vlan: ensure sufficient headroom in vlan_dev_hard_header() 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-617

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 after the outer VLAN header has been pushed.

A flaw was found in the Linux kernel's virtual local area network (VLAN) driver. When processing network packets that lack sufficient reserved buffer space (headroom) before network headers are appended, the system triggers a panic condition. An attacker could exploit this vulnerability to cause a Denial of Service (DoS) by crashing the system.

Red Hat rates this vulnerability as Moderate because it is confined to a local denial-of-service condition without compromising system integrity or confidentiality. The issue arises during packet transmission over VLAN interfaces when buffer headroom becomes insufficient during dynamic device adjustments or with specific frame types, triggering a kernel panic. Exploitation requires local authenticated access with permissions to transmit specific frame types or reconfigure network devices, thereby limiting the overall blast radius. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Fix deferred kernel Red Hat Enterprise Linux 7 Fix deferred kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-98554 https://nvd.nist.gov/vuln/detail/CVE-2026-98554 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98554.mbox