CVE-2026-31737: Linux Kernel ftgmac100 resource leak in ring allocation failure

CVE-2026-31737 · Severity: medium · CVSS 5.5 · Published 2026-05-01

A memory leak vulnerability was identified in the Linux kernel's Faraday FTGMAC100 ethernet driver, which is used in various industrial networking components including certain Siemens SIMATIC controllers. If the driver fails to initialize properly, it may fail to release previously allocated memory, leading to a gradual depletion of system resources. In practice, this could allow a local attacker to cause a denial-of-service condition, potentially impacting the availability of industrial control operations.

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

Quick answers

Is CVE-2026-31737 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-31737 being exploited in the wild.
How severe is CVE-2026-31737?
Medium severity, with a CVSS score of 5.5, published 1 May 2026.
Which products and versions are affected?
Linux Kernel ftgmac100 driver; 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.
Is there a fix for CVE-2026-31737?
A patch was published on 2026-04-18: Committed to Linux stable tree by Greg Kroah-Hartman Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-31737 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-31737?
Check whether you run Linux Kernel, Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A vulnerability exists in the ftgmac100_alloc_rings() function within the Faraday FTGMAC100 ethernet driver (drivers/net/ethernet/faraday/ftgmac100.c). The function allocates multiple resources (rx_skbs, tx_skbs, rxdes, txdes, and rx_scratch) in stages; however, if an intermediate allocation fails, the function returns -ENOMEM immediately without unwinding or freeing previously allocated resources. This results in a kernel memory leak. A local attacker could potentially trigger repeated interface open/close cycles to exhaust system memory, leading to a denial-of-service (DoS). The fix introduces staged local unwind labels to ensure all resources are freed in reverse order upon failure.

Affected products

  • Linux Linux Kernel ftgmac100 driver
  • 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 Yufan Chen
  • 2026-04-18: patched: Committed to Linux stable tree by Greg Kroah-Hartman
  • 2026-05-01: advisory: CVE published to NVD

References

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