Junglewise Threat Intelligence

CVE-2026-23392: Linux Kernel netfilter use-after-free in nf_tables flowtable error path

CVE-2026-23392 · Severity: high · CVSS 7.8 · Published 2026-03-25

Technologies: Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP, Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP, Linux Kernel, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP. Vendors: Siemens, Linux.

Executive brief

A vulnerability exists in the Linux kernel's networking subsystem (netfilter) that could allow a local user to crash the system or potentially execute unauthorized code. The issue occurs when the system fails to properly clean up network flow tables during specific error conditions, leading to memory corruption. This affects Linux-based systems and certain industrial Siemens controllers that utilize the affected kernel versions.

Technical details

A use-after-free (UAF) vulnerability exists in net/netfilter/nf_tables_api.c within the Linux kernel. The root cause is the failure to call synchronize_rcu() during the error path of nf_tables_newflowtable when unregistering hooks. This allows a flowtable to be released while it is still being accessed by the packet path or nfnetlink_hook control plane. An attacker with local access can trigger this rare error path (e.g., by reaching maximum hook limits or forcing hardware offload failures) to cause memory corruption. The vulnerability was identified via KASAN during hook dumping operations. Patches have been released across multiple stable kernel branches to ensure proper RCU grace period synchronization.

Affected products

  • Linux Linux Kernel Fixed in versions 7e3955b, adee343, c8092ed, d2632de, d73f4b5, e78a2dcc
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5, V3.1.6
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6

Timeline

  • 2026-03-17: other: Patch authored by Pablo Neira Ayuso
  • 2026-03-25: advisory: Initial publication of CVE-2026-23392
  • 2026-07-14: other: Siemens updated advisory with affected industrial products

References

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