Linux Kernel up to 7.2.2 VLAN af_packet.c vlan_transfer_features hard_header_len race condition

Summaryinfo

A vulnerability classified as problematic was found in Linux Kernel up to 7.2.2. This impacts the function vlan_transfer_features of the file af_packet.c of the component VLAN. Such manipulation of the argument hard_header_len leads to race condition. This vulnerability is listed as CVE-2026-80925. The attack must be carried out locally. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.2 and classified as problematic. Affected by this issue is the function vlan_transfer_features of the file af_packet.c of the component VLAN. The manipulation of the argument hard_header_len with an unknown input leads to a race condition vulnerability. Using CWE to declare the problem leads to CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. Impacted is integrity, and availability. CVE summarizes:

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")

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-80925 since 08/26/2026. The exploitation is known to be easy. The attack needs to be approached locally. Additional levels of successful authentication are necessary for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 7.2.3 or 7.3-rc1 eliminates this vulnerability. Applying the patch a29f3b884ba50217e6f50414f568073221e2bb07/447cbe95ebb95392b5d8f6a01c0556826919ce23 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2

License

• open-source

Website

• Vendor: https://www.kernel.org/

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