# Siemens S7-1500 CPU Linux Subsystem Riddled With CVEs

Published: 2026-07-28 · Severity: medium · Sectors: manufacturing
Canonical: https://vorant.io/reports/d8411d12-d36e-5a73-ad32-69bf1f674b5b/siemens-s7-1500-cpu-linux-subsystem-riddled-with-cves

> Siemens disclosed hundreds of vulnerabilities in the GNU/Linux subsystem of SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP firmware, with fixes still pending for many.

CISA and Siemens published an ICS advisory covering the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP (including SIPLUS variants), identifying an extremely large number of vulnerabilities—several hundred CVEs—in the additional GNU/Linux subsystem bundled with firmware version V3.1.6 and later. The vast majority of these CVEs stem from upstream Linux kernel and open-source component issues (memory corruption, use-after-free, out-of-bounds access, privilege escalation, etc.) that have accumulated over multiple years of kernel releases, rather than vulnerabilities unique to Siemens' own code.

One specifically called-out issue, CVE-2021-41617, involves an OpenSSH privilege escalation flaw where supplemental groups are not properly initialized when AuthorizedKeysCommand or AuthorizedPrincipalsCommand helper programs are configured to run as a different user, potentially granting those helpers unintended group privileges. Siemens states that fix versions are still being prepared for many of the affected CVEs and is recommending interim countermeasures (network segmentation, restricting access to the Linux subsystem, and following general ICS hardening guidance) until patches are released.

The affected products are deployed worldwide in critical manufacturing environments. There is no indication in the advisory of active exploitation in the wild; this is a vendor-driven vulnerability disclosure requiring asset owners to inventory affected CPU models, monitor for Siemens patch releases, and apply the recommended mitigations in the interim.

## Mentioned in this report

- Vulnerabilities: CVE-2021-41617

1 more detection artefacts for this report (IOC-atomic rules, Splunk/KQL/Elastic conversions, YARA, Suricata) are available to subscribers.

Source reporting: https://www.cisa.gov/news-events/ics-advisories/icsa-26-209-04

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