Junglewise Threat Intelligence

CVE-2026-43035: Linux kernel information leak in tc_chain_fill_node

CVE-2026-43035 · Severity: medium · CVSS 5.5 · Published 2026-05-01

Executive brief

A vulnerability in the Linux kernel's networking subsystem could allow a local user to access sensitive information from the system's memory. This occurs because certain internal messages were not properly cleared before being sent to user-accessible areas. While this specific flaw primarily impacts system privacy, it could potentially be used to facilitate more complex attacks against the operating system or affected industrial hardware.

Technical details

An information leak vulnerability exists in the Linux kernel's net/sched/cls_api.c component due to an uninitialized resource (CWE-908). The function tc_chain_fill_node() fails to initialize the tcm_info field of the tcmsg structure. Because the underlying memory allocation is not zeroed, 4 bytes of kernel heap memory are leaked to userspace when netlink messages are constructed. A local attacker with basic privileges can exploit this to read sensitive kernel memory. The issue has been resolved in multiple stable kernel branches by explicitly zeroing the tcm_info field.

Affected products

  • Linux Linux Kernel
  • 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

  • 2026-03-29: disclosed: Initial patch authored by Yochai Eisenrich
  • 2026-04-11: patched: Patches committed to stable kernel trees
  • 2026-05-01: advisory: CVE published to NVD
  • 2026-07-14: advisory: Siemens updated advisory with affected industrial products

References

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