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PatchSiren cyber security CVE debrief

CVE-2024-6387 Siemens CVE debrief

CVE-2024-6387 is a high-severity OpenSSH server regression that Siemens and CISA associate with selected SIMATIC S7-1500 CPU family products. The issue is a race condition in sshd signal handling that an unauthenticated remote attacker may be able to trigger by failing to authenticate within a set time period. The supplied advisory states that no fix is currently available for the affected Siemens products, so exposure reduction and strict access control are the primary defenses.

Vendor
Siemens
Product
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2024-07-01
Original CVE updated
2026-09-01
Advisory published
2024-07-01
Advisory updated
2026-09-01

Who should care

OT and ICS operators using the affected Siemens SIMATIC S7-1500 CPU 1518/1518F MFP variants, defenders responsible for the additional GNU/Linux subsystem interactive shell, and teams managing remote access paths into industrial control environments.

Technical summary

The advisory describes a security regression in OpenSSH's server (sshd), linked to CVE-2006-5051, where a race condition can cause unsafe signal handling. The stated trigger is an unauthenticated remote attacker causing repeated authentication failure within a timing window. Siemens' remediation guidance for the affected products focuses on limiting access to the interactive shell of the additional GNU/Linux subsystem to trusted personnel and only building/running applications from trusted sources; the advisory also states that currently no fix is available.

Defensive priority

High priority. Because the issue is remotely triggerable without authentication and the advisory indicates no available fix for the affected Siemens products, organizations should prioritize access restriction, exposure review, and compensating controls.

Recommended defensive actions

  • Restrict access to the interactive shell of the additional GNU/Linux subsystem to trusted personnel only.
  • Only build and run applications from trusted sources on the affected systems.
  • Review whether the affected SIMATIC S7-1500 CPU variants are exposed to untrusted network access paths.
  • Apply Siemens and CISA guidance from the linked advisories and monitor for future vendor updates.
  • Treat the affected systems as needing compensating controls because the supplied advisory states that no fix is currently available.

Evidence notes

CISA's CSAF advisory ICSA-25-162-05 identifies the affected Siemens SIMATIC S7-1500 CPU family products and records the OpenSSH sshd race condition description. The supplied remediation entries explicitly say to limit interactive-shell access and to use trusted sources only, and they also state that currently no fix is available. The supplied enrichment marks this as not a KEV-listed issue.

Sources and references

Verified primary and authoritative sources

  • CVE-2024-6387 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2024-6387

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2024-6387 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2024-6387

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/OT/white/2025/icsa-25-162-05.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-082556.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-082556.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-25-162-05

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-alerts/ics-alert-10-301-01

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/resources-tools/resources/ics-recommended-practices

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/topics/industrial-control-systems

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf

    Reference

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.