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PatchSiren cyber security CVE debrief

CVE-2020-26143 Siemens CVE debrief

CVE-2020-26143 is described in the supplied CISA/Siemens advisory corpus as a wireless integrity issue affecting multiple Siemens SCALANCE devices. The advisory says the WEP, WPA, WPA2, and WPA3 implementations accept fragmented plaintext frames in a protected Wi‑Fi network, which can let an adversary inject arbitrary data frames independent of the network configuration. The corpus also states that exploitation is limited to Wi‑Fi range and that Siemens provides a fix in V6.6.0 or later.

Vendor
Siemens
Product
SCALANCE W721-1 RJ45 (6GK5721-1FC00-0AA0)
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-14
Original CVE updated
2026-04-21
Advisory published
2026-04-14
Advisory updated
2026-04-21

Who should care

OT/ICS operators, engineers, and security teams responsible for the listed Siemens SCALANCE wireless devices, especially where wireless coverage reaches beyond tightly controlled areas.

Technical summary

The advisory describes an integrity flaw in wireless protocol handling: fragmented plaintext frames are accepted inside protected Wi‑Fi networks, allowing frame injection without dependence on the specific network configuration. The supplied corpus associates the issue with Siemens SCALANCE wireless products and recommends updating to V6.6.0 or later. The mitigation text also notes the attack requires Wi‑Fi range, making wireless exposure and physical placement relevant risk factors.

Defensive priority

Medium. Prioritize remediation in the next planned maintenance cycle, and accelerate if the devices are reachable from uncontrolled wireless areas or support critical traffic.

Recommended defensive actions

  • Update affected Siemens SCALANCE devices to V6.6.0 or later, per the advisory.
  • Reduce Wi‑Fi transmission power where feasible to limit attack reach.
  • Place devices in private areas with physical access controls when possible.
  • Review wireless exposure for the listed SCALANCE models and limit coverage beyond necessary areas.
  • Use the provided Siemens and CISA advisory references to confirm model coverage and maintenance planning.

Evidence notes

The source corpus is a CISA CSAF advisory (ICSA-26-111-07) republishing Siemens ProductCERT SSA-019200 content. It lists many affected SCALANCE W721/W722/W734/W738/W748/W761/W774/W778/W786/W788 variants and states the fix is V6.6.0 or later. The remediation text explicitly says the vulnerabilities can only be exploited within Wi‑Fi range and recommends reducing transmission power or using private areas with physical access controls. The corpus also contains inconsistent ALFA Windows driver wording in the CVE description; product scope and remediation were taken from the Siemens CSAF advisory fields and references.

Sources and references

Verified primary and authoritative sources

  • CVE-2020-26143 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2020-26143

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

  • CVE-2020-26143 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2020-26143

    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-26-111-07.json

    cisa_csaf

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/csaf/ssa-019200.json

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://cert-portal.siemens.com/productcert/html/ssa-019200.html

    Reference

  • Source reference

    Unverified legacy reference

    URL: https://www.cisa.gov/news-events/ics-advisories/icsa-26-111-07

    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.