{"cve":"CVE-2026-80925","nvd":{"published":"2026-09-09T17:17:47.763","modified":"2026-10-19T09:17:23.433","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvlan: fix skb_under_panic and races when toggling HW VLAN offload\n\nToggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or\nNETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(),\nwhich dynamically changed vlandev->hard_header_len.\n\nThis causes two issues:\n1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2)\n   read dev->hard_header_len without holding RTNL lock. Mutating\n   hard_header_len dynamically under RTNL creates a data race where upper\n   layers reserve insufficient headroom based on a stale hard_header_len,\n   resulting in skb_under_panic when vlan_dev_hard_header() is called.\n2. In addition, vlan_transfer_features() updated hard_header_len without\n   updating header_ops, causing a mismatch between allocated headroom\n   and header creation.\n\nAlways setting dev->hard_header_len = real_dev->hard_header_len and\ndev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally\nensures:\n- dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len,\n  eliminating all dynamic runtime updates and data races on hard_header_len.\n- Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve\n  sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len +\n  real_dev->needed_headroom + VLAN_HLEN).\n- vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV\n  requirements are honored.\n- AF_PACKET SOCK_RAW network header offsets remain correctly aligned at\n  real_dev->hard_header_len.\n- vlan_header_ops is used unconditionally.\n\nNote to stable teams: Make sure to backport these commits:\n\ne16e960d55a4 (\"ipvlan: inherit needed_headroom and needed_tailroom from phy_dev\")\ncef51860becd (\"macvlan: inherit needed_headroom and needed_tailroom from lowerdev\")","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/1517d1996b5236fe69eccd9d253f725e06996eb1","https://git.kernel.org/stable/c/447cbe95ebb95392b5d8f6a01c0556826919ce23","https://git.kernel.org/stable/c/a29f3b884ba50217e6f50414f568073221e2bb07","https://git.kernel.org/stable/c/b30fe4de285b9bdaf9508740191f69f7cd83b8fa","https://git.kernel.org/stable/c/b38d7a4bc9c17e1d437696da25f9fbc286614d9d"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:52:53.108888569+00:00"},"epss":{"cve":"CVE-2026-80925","score":0.00156,"percentile":0.04729,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}