Security readout for executives and security teams
Plain-English summary
This vulnerability affects WAGO I/O-Check Service on listed WAGO product families. A remote unauthenticated attacker could send malicious network traffic that crashes the iocheck process and can write memory, creating integrity loss and denial of service risk in operational environments.
Executive priority
Treat this as high-priority for OT sites using the listed WAGO devices. Focus first on asset discovery and network isolation, then follow vendor remediation guidance. Do not assume active exploitation without new evidence.
Technical view
CVE-2021-34566 is a CWE-120 memory overflow in WAGO I/O-Check Service. The CVSS 3.1 score is 9.1, with network attack vector, low complexity, no privileges, and no user interaction. Reported impacts are high integrity and availability, with no confidentiality impact stated.
Likely exposure
Exposure is most likely where affected WAGO 750-81xx, 750-82xx, 752-8303/8000-0002, or 762-series FW1 devices have I/O-Check Service reachable from untrusted or poorly segmented networks.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The risk remains serious because the described attack is unauthenticated, network reachable, and can affect integrity and availability.
Researcher notes
The public bundle names memory overflow and OS-command-containing crafted packets but does not provide patch detail in the supplied text. Avoid extrapolating affected versions beyond the listed WAGO product families and FW1 entries.
Mitigation direction
- Review WAGO or VDE-2020-036 guidance for vendor-approved fixes or mitigations.
- Inventory listed WAGO product families and confirm firmware versions.
- Restrict I/O-Check Service access to trusted management networks only.
- Block exposure from the internet and non-operational user networks.
- Plan firmware remediation only according to vendor instructions.
Validation and detection
- Identify all deployed WAGO devices matching the listed product families.
- Confirm whether FW1 and I/O-Check Service are present.
- Check network paths to the service from untrusted segments.
- Review operational logs for iocheck crashes or unexpected restarts.
- Verify segmentation rules block unauthorized access.
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.
CWE-120: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-34566 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
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H3.95.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://cert.vde.com/en/advisories/VDE-2020-036/CVE reference
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.
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.