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

vlan: fix skb_under_panic and races when toggling HW VLAN offload

Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or
NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(),
which dynamically changed vlandev->hard_header_len.

This causes two issues:
1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2)
read dev->hard_header_len without holding RTNL lock. Mutating
hard_header_len dynamically under RTNL creates a data race where upper
layers reserve insufficient headroom based on a stale hard_header_len,
resulting in skb_under_panic when vlan_dev_hard_header() is called.
2. In addition, vlan_transfer_features() updated hard_header_len without
updating header_ops, causing a mismatch between allocated headroom
and header creation.

Always setting dev->hard_header_len = real_dev->hard_header_len and
dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally
ensures:
- dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len,
eliminating all dynamic runtime updates and data races on hard_header_len.
- Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve
sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len +
real_dev->needed_headroom + VLAN_HLEN).
- vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV
requirements are honored.
- AF_PACKET SOCK_RAW network header offsets remain correctly aligned at
real_dev->hard_header_len.
- vlan_header_ops is used unconditionally.

Note to stable teams: Make sure to backport these commits:

e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev")
cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev")

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

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This CVE is not in the KEV list.

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Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
Linux Linux unaffected
Version Status Constraints
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 affected < a29f3b884ba50217e6f50414f568073221e2bb07
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 affected < 447cbe95ebb95392b5d8f6a01c0556826919ce23
Linux Linux affected
Version Status Constraints
2.6.12 affected —
0 unaffected < 2.6.12
7.2.3 unaffected ≤ 7.2.*
7.3-rc1 unaffected ≤ *

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https://git.kernel.org/stable/c/447cbe95ebb95392b5d8f6a01c0556826919ce23 cve-icon cve-icon
https://git.kernel.org/stable/c/a29f3b884ba50217e6f50414f568073221e2bb07 cve-icon cve-icon
History

Wed, 09 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: vlan: fix skb_under_panic and races when toggling HW VLAN offload Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(), which dynamically changed vlandev->hard_header_len. This causes two issues: 1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2) read dev->hard_header_len without holding RTNL lock. Mutating hard_header_len dynamically under RTNL creates a data race where upper layers reserve insufficient headroom based on a stale hard_header_len, resulting in skb_under_panic when vlan_dev_hard_header() is called. 2. In addition, vlan_transfer_features() updated hard_header_len without updating header_ops, causing a mismatch between allocated headroom and header creation. Always setting dev->hard_header_len = real_dev->hard_header_len and dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally ensures: - dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len, eliminating all dynamic runtime updates and data races on hard_header_len. - Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len + real_dev->needed_headroom + VLAN_HLEN). - vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV requirements are honored. - AF_PACKET SOCK_RAW network header offsets remain correctly aligned at real_dev->hard_header_len. - vlan_header_ops is used unconditionally. Note to stable teams: Make sure to backport these commits: e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev") cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev")
Title vlan: fix skb_under_panic and races when toggling HW VLAN offload
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-09T16:19:44.748Z

Reserved: 2026-08-26T14:34:25.802Z

Link: CVE-2026-80925

cve-icon Vulnrichment

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cve-icon NVD

Status : Received

Published: 2026-09-09T17:17:47.763

Modified: 2026-09-09T17:17:47.763

Link: CVE-2026-80925

cve-icon Redhat

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cve-icon OpenCVE Enrichment

Updated: 2026-09-09T18:00:08Z

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