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PatchSiren cyber security CVE debrief

CVE-2022-0778 Siemens CVE debrief

CVE-2022-0778 affects Siemens SCALANCE wireless devices that use OpenSSL during certificate or key parsing. A malformed certificate or private key with invalid explicit elliptic curve parameters can trigger an infinite loop in BN_mod_sqrt(), creating a denial-of-service condition. Siemens’ advisory maps the issue to multiple SCALANCE W7xx/W78x device variants and recommends upgrading to version 6.6.0 or later.

Vendor
Siemens
Product
SCALANCE W721-1 RJ45 (6GK5721-1FC00-0AA0)
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2025-08-12
Original CVE updated
2025-08-12
Advisory published
2025-08-12
Advisory updated
2025-08-12

Who should care

OT and industrial network operators using affected Siemens SCALANCE wireless devices; administrators who import, validate, or manage external certificates and keys; and teams responsible for device firmware maintenance in environments that rely on certificate-based access or trust stores.

Technical summary

The underlying flaw is in OpenSSL’s BN_mod_sqrt() handling of non-prime moduli. When certificate parsing reaches code paths for elliptic curve public keys in compressed form or explicit elliptic curve parameters, a crafted certificate or private key can cause the function to loop forever. Because parsing occurs before certificate signature verification, simply presenting a maliciously crafted object to a susceptible parser can be enough to cause a denial-of-service event.

Defensive priority

High. The published CVSS score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), and the main operational risk is service hang or parser lockup on externally supplied certificate/key content.

Recommended defensive actions

  • Upgrade affected Siemens SCALANCE devices to V6.6.0 or later, as directed by Siemens.
  • Inventory SCALANCE models and firmware versions against the affected product list in the advisory before maintenance windows.
  • Limit exposure to untrusted certificate and private-key inputs wherever operationally possible, especially in workflows that ingest externally supplied material.
  • Validate certificate and key handling paths in OT operations plans so a hang in parsing does not disrupt critical availability or recovery procedures.

Evidence notes

The source corpus links the vulnerability description to the Siemens SCALANCE advisory ICSA-26-111-07 / SSA-019200, which states that affected products run versions earlier than 6.6.0 and that remediation is to update to 6.6.0 or later. The advisory also states the issue can be reached while parsing crafted certificates or private keys containing explicit elliptic curve parameters. CISA’s source item revision history shows publication on 2026-04-14 and a CISA republication on 2026-04-21.

Sources and references

Verified primary and authoritative sources

  • CVE-2022-0778 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2022-0778

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

  • CVE-2022-0778 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2022-0778

    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.