CVE-2026-98526
Received Received - Intake

LLC Frame Headroom Underflow in Linux Kernel

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
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.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98526
EUVD
EUVD-2026-103571

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux bf9ae5386bca8836c16e69ab8fdbe46767d7452a
Linux Linux 2.6.34

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Exploitability

CWE
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves insufficient headroom reservation in LLC frame allocation. When using stacked Ethernet devices like VLAN devices, the LLC response can underflow skb headroom because the VLAN header pushes additional data before the Ethernet header. The fix uses LL_RESERVED_SPACE() to account for the actual required headroom while keeping the LLC device-type check.

Detection Guidance

This vulnerability affects the Linux kernel's LLC frame handling, particularly with stacked Ethernet devices like VLANs. Detection requires checking kernel versions and LLC-related configurations. Use 'uname -a' to verify kernel version and 'ip link show' to inspect network interfaces for VLAN or stacked devices. Monitor kernel logs for LLC-related errors or crashes.

Impact Analysis

This vulnerability may cause network packet corruption or crashes in systems using VLAN devices with LLC protocols. It could lead to denial-of-service conditions or unexpected behavior in affected Linux kernel versions.

Mitigation Strategies

Apply the latest kernel patches from your Linux distribution to resolve the LLC headroom issue. If patches are unavailable, avoid using VLAN devices or stacked Ethernet configurations until an update is applied. Monitor vendor advisories for updates.

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