Executive brief
A vulnerability exists in the Linux kernel's networking subsystem (Netfilter) that could allow a local attacker to crash the system or potentially execute unauthorized code. The issue occurs when the system incorrectly handles the deletion of network timeout rules, leading to a memory error. This affects various Linux-based systems, including certain industrial controllers from Siemens, and could impact system stability and availability.
Technical details
A use-after-free vulnerability exists in the nft_ct_timeout_obj_destroy() function within the Linux kernel's Netfilter subsystem. The root cause is that the timeout object is freed using kfree() immediately after nf_ct_untimeout() without waiting for an RCU grace period, while concurrent CPUs may still hold RCU-protected references. An attacker with local access can trigger this race condition during concurrent packet processing, leading to memory corruption (as seen in KASAN reports in nf_conntrack_tcp_packet). This can result in a kernel crash or arbitrary code execution. The fix involves adding an rcu_head to the nf_ct_timeout structure and using kfree_rcu() to defer freeing.
Affected products
- Linux Linux Kernel Fixed in various stable branches including 5.10.y, 5.15.y, 6.1.y, 6.6.y, 6.8.y, 6.9.y
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
Timeline
- 2026-04-03: other: Patch authored
- 2026-04-24: advisory: NVD publication date
- 2026-07-14: other: Siemens advisory enrichment added to CVE record
References
- https://git.kernel.org/stable/c/070abdf1b04325b21a20a2a0c39a2208af107275
- https://git.kernel.org/stable/c/aa7cfa16f98f8ec3e6d47c34e1a8c1ae4b9b8b77
- https://git.kernel.org/stable/c/b42aca3660dc2627a29a38131597ca610dc451f9
- https://git.kernel.org/stable/c/c458fc1c278a65ad5381083121d39a479973ebed
- https://git.kernel.org/stable/c/c581e5c8f2b59158f62efe61c1a3dc36189081ff
- https://git.kernel.org/stable/c/d0983b48c10d1509fd795c155f8b1e832e1369ff
- https://git.kernel.org/stable/c/f16fe84879a5280f05ebbcea593a189ba0f3e79a