CVE-2019-6856 — A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability ex

A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service when writing specific physical memory block

01What is this vulnerability?

A CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service when writing specific physical memory blocks using Modbus TCP.

02Affected products

No structured affected-product list available — see references below for vendor advisories.

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-01-06T23:15:11.317
• Last modified: 2026-05-29T15:16:17.880

09References

• www.se.com — https://www.se.com/ww/en/download/document/SEVD-2019-344-01
• www.us-cert.gov — https://www.us-cert.gov/ics/advisories/icsa-20-016-01
• www.se.com — https://www.se.com/ww/en/download/document/SEVD-2019-344-01
• www.us-cert.gov — https://www.us-cert.gov/ics/advisories/icsa-20-016-01