---
id: "CVE-2026-98526"
kind: "vulnerability"
aliases: ["CVE-2026-98526"]
title: "Linux kernel: LLC frames on VLAN devices can underflow packet headroom"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kernel", "linux", "llc", "runtime", "vlan"]
not_affected_if: []
published_at: "2026-10-18T16:17:04+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:25:07+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98526", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel: LLC frames on VLAN devices can underflow packet headroom

The Linux kernel's LLC frame allocator reserves too little link-layer headroom for stacked Ethernet devices such as VLAN interfaces. An LLC response sent on such a device can underflow the socket buffer headroom in eth_header().

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98526

## From the sources

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

llc: reserve device headroom for allocated frames

llc_alloc_frame() reserves link-layer headroom using the device type.
This is insufficient for stacked Ethernet devices such as VLAN devices,
where vlan_dev_hard_header() pushes a VLAN header before the lower
device's Ethernet header. An LLC response on such a device can
therefore underflow skb headroom in eth_header().

Use LL_RESERVED_SPACE() to account for the device's actual required
headroom while preserving the existing LLC device-type check.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_