Security readout for executives and security teams
Plain-English summary
This issue can make supported Schneider Modicon PLC families stop responding or enter a denial-of-service condition when malformed or integrity-failing file activity is sent over Modbus. For businesses using these controllers in production environments, the main concern is operational disruption, not data theft.
Executive priority
Treat this as a high-priority OT resilience issue where affected controllers support critical operations. Prioritize sites where Modbus is reachable beyond tightly controlled engineering networks.
Technical view
CVE-2018-7849 is described as CWE-248, an uncaught exception, in all versions of Modicon M580, M340, Quantum, and Premium controllers. The reported trigger is improper data-integrity handling during file transfer activity over Modbus, causing possible denial of service.
Likely exposure
Exposure is most relevant where affected Modicon controllers allow Modbus communication from engineering workstations, operations networks, remote access paths, or poorly segmented IT networks. The source bundle does not provide internet-exposure evidence.
Exploitation context
The bundle does not show CISA KEV listing or active exploitation evidence. Public disclosure exists through Schneider Electric advisory SEVD-2019-134-11 and Talos TALOS-2018-0737, so defenders should assume technical details may be known.
Researcher notes
Evidence is limited in the provided bundle: no CVSS vector, no named fixed versions, and no confirmed exploitation. Analysis should stay anchored to the Schneider advisory, Talos report, and local exposure to Modbus-accessible controller file operations.
Mitigation direction
- Review Schneider advisory SEVD-2019-134-11 for vendor-approved fixes or compensating controls.
- Inventory Modicon M580, M340, Quantum, and Premium controllers.
- Restrict Modbus access to trusted engineering and operations systems only.
- Segment affected controllers from corporate and internet-facing networks.
- Monitor for abnormal controller faults or unexpected Modbus file-transfer activity.
Validation and detection
- Confirm whether the named Modicon controller families exist in OT asset inventory.
- Identify all systems permitted to communicate with those controllers over Modbus.
- Compare controller firmware and configuration status against Schneider guidance.
- Review OT logs for unexplained controller faults or denial-of-service symptoms.
- Validate network segmentation blocks untrusted Modbus paths.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2018-7849 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.schneider-electric.com/en/download/document/SEVD-2019-134-11/CVE reference · x_refsource_MISC
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2018-0737CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.