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CVE-2025-40805 Siemens CVE debrief

CVE-2025-40805 is a critical authentication-bypass flaw in Siemens Industrial Edge and related Siemens industrial products. According to CISA’s CSAF republication of Siemens ProductCERT advisory SSA-001536, affected devices do not properly enforce user authentication on specific API endpoints. A remote attacker who already knows the identity of a legitimate user may be able to bypass authentication and impersonate that user. The issue was published on 2026-01-13 and most recently updated on 2026-05-14, when CISA republished Siemens’ updated guidance and added a fix for the SIMATIC Automation Workstation family. The advisory rates the issue CVSS 3.1 10.0/Critical (AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H).

Vendor
Siemens
Product
Industrial Edge Cloud Device (IECD)
CVSS
CRITICAL 10
CISA KEV
Not listed in stored evidence
Original CVE published
2026-01-13
Original CVE updated
2026-05-14
Advisory published
2026-01-13
Advisory updated
2026-05-14

Who should care

Siemens Industrial Edge operators, OT/ICS security teams, plant administrators, and anyone managing the Siemens product families named in the advisory—especially Internet- or enterprise-connected deployments that expose management APIs.

Technical summary

The vulnerability is an authentication control failure on specific API endpoints. If an attacker learns a valid user identity, they may be able to submit unauthenticated requests that are treated as belonging to that user, enabling impersonation and follow-on unauthorized actions. The source advisory ties the flaw to Siemens Industrial Edge Cloud Device (IECD) and additional Siemens industrial product families listed in the CSAF, with vendor-fixed versions provided per product.

Defensive priority

Immediate. This is a network-reachable, no-privileges-required, critical-severity authentication bypass affecting industrial products. Prioritize patching to vendor-fixed versions and reduce exposure until upgrades are complete.

Recommended defensive actions

  • Upgrade affected Siemens products to the vendor-fixed version that applies to your model and deployment.
  • For Industrial Edge Cloud Device / related Industrial Edge products, apply Siemens’ fixed release guidance in the advisory and associated release notes; do not assume one version fits all product families.
  • If you cannot patch immediately, restrict network access to affected devices so only trusted parties can reach management/API endpoints.
  • Review whether any exposed API endpoints are reachable from broader OT, IT, or remote-access networks and tighten segmentation accordingly.
  • Validate local and remote account inventories because the attack condition depends on knowing a legitimate user identity.
  • Monitor Siemens and CISA advisory updates for product-specific remediation changes, especially if you operate SIMATIC Automation Workstation or other listed families.

Evidence notes

Primary evidence comes from the CISA CSAF advisory ICSA-26-015-08, which republishes Siemens ProductCERT SSA-001536. The advisory description states that specific API endpoints do not properly enforce user authentication and that successful exploitation requires knowledge of a legitimate user identity. The CSAF revision history shows the original publication on 2026-01-13 and the latest republication update on 2026-05-14. Remediation entries provide vendor-fixed versions and a network-access restriction mitigation.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-40805 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-40805

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

  • CVE-2025-40805 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-40805

    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/2026/icsa-26-015-08.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-001536.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-001536.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-015-08

    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.