Executive brief
A vulnerability was identified in the Linux kernel's networking subsystem (netfilter) that could allow a local user to cause a system crash. The issue stems from how the system handles specific network filtering instructions that are not intended for direct use. This could lead to a denial-of-service condition, impacting the availability of affected systems, including certain industrial controllers.
Technical details
A vulnerability in the Linux kernel netfilter subsystem (nf_tables) exists because the nft_verdict_init function in net/netfilter/nf_tables_api.c did not properly validate NF_QUEUE verdicts. While NF_QUEUE is intended to be delivered via the nft_queue expression, an attacker could provide an immediate NF_QUEUE verdict. This is particularly problematic in the ARP family, which does not support queuing but could still reach this code path. A local attacker with sufficient privileges to modify nftables rules can exploit this to trigger unexpected kernel behavior or a denial-of-service (DoS). The issue has been resolved by explicitly rejecting immediate NF_QUEUE verdicts in the verdict initialization logic.
Affected products
- Linux Linux Kernel All versions prior to the April 2026 patches
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
Timeline
- 2026-03-31: other: Patch authored by Pablo Neira Ayuso
- 2026-05-01: disclosed
- 2026-05-01: advisory
References
- https://git.kernel.org/stable/c/17dc5d5a935c771338430cbc156a16a51cfd31e8
- https://git.kernel.org/stable/c/2f7f825a548be55420f0f5f716f6c27b9d312d3f
- https://git.kernel.org/stable/c/42a47f4b1b7695026ab9bc1bb35d4622b0835c95
- https://git.kernel.org/stable/c/4b12a3cc3f075e750cc3c5e693fd25fb400af4a2
- https://git.kernel.org/stable/c/68390437a998c3f2c57212b413abef5e6d657d88
- https://git.kernel.org/stable/c/da107398cbd4bbdb6bffecb2ce86d5c9384f4cec
- https://git.kernel.org/stable/c/f140593901724cfbd16597c3a4fcb24a58ae44b0