Junglewise Threat Intelligence

CVE-2026-31391: Linux Kernel resource leak in Atmel SHA204A driver

CVE-2026-31391 · Severity: medium · CVSS 5.5 · Published 2026-04-03

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 in the Linux kernel's Atmel SHA204A driver could allow a local user to cause a denial-of-service condition. The issue occurs when the system runs out of memory, causing a counter to be incorrectly handled and blocking future hardware random number generator operations. This affects certain industrial control systems, such as Siemens SIMATIC S7-1500 CPUs, that rely on this kernel component.

Technical details

A reference count leak exists in drivers/crypto/atmel-sha204a.c within the atmel_sha204a_rng_read_nonblocking function. When a memory allocation for work_data fails (ENOMEM), the driver fails to decrement the tfm_count counter. This results in a permanent increment that eventually blocks subsequent reads from the hardware random number generator (hwrng). The vulnerability requires local access to trigger and results in a loss of availability for the affected cryptographic component. Patches have been released across multiple stable Linux kernel branches.

Affected products

  • Linux Linux Kernel da001fb651b0 to c2d0c45dbb9eb272385ae919b17eef5a5318d3f8
  • 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

  • 2026-03-18: disclosed: Initial patch authored by Thorsten Blum
  • 2026-03-25: patched: Commits merged into stable kernel trees
  • 2026-04-03: advisory: CVE published to NVD

References

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