CVE-2026-43033: Linux Kernel memory corruption in crypto authencesn decryption

CVE-2026-43033 · Severity: high · CVSS 7.8 · Published 2026-05-01

A vulnerability exists in the Linux kernel's cryptographic subsystem, specifically affecting how certain encrypted data is processed. This issue could allow a local attacker to cause a system crash or potentially gain unauthorized access to sensitive information. The flaw impacts various systems using the Linux kernel, including specific industrial automation controllers from Siemens.

Technologies: 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: Siemens.

Quick answers

Is CVE-2026-43033 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-43033 being exploited in the wild.
How severe is CVE-2026-43033?
High severity, with a CVSS score of 7.8, published 1 May 2026.
Which products and versions are affected?
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-2026-43033?
A patch was published on 2026-03-27: Initial patch authored by Herbert Xu Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-43033 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-43033?
Check whether you run Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP, Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP or Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP 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

The vulnerability is located in the crypto/authencesn.c component of the Linux kernel. It stems from improper handling of high-order sequence bits (hiseq) during out-of-place decryption (where the source and destination buffers differ). Specifically, the code incorrectly placed these bits at the end of the destination buffer, which was unnecessary and led to incorrect data rearrangement for hashing. An attacker with local access could exploit this logic error to trigger memory corruption or bypass cryptographic protections. Patches have been released across multiple stable kernel branches to ensure proper buffer handling and data alignment during the decryption process.

Affected products

  • Linux Linux crypto/authencesn.c
  • 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

  • 2026-05-01: disclosed: Vulnerability published in NVD
  • 2026-03-27: patched: Initial patch authored by Herbert Xu

References

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