Security readout for executives and security teams
Plain-English summary
Some Weidmüller industrial controllers and IoT gateways expose a network port that was meant to be internal only. An unauthenticated network attacker may be able to manipulate the device or stop its operation, creating a serious operational availability and integrity risk.
Executive priority
Treat this as a high-priority OT exposure issue. It affects device integrity and availability, does not require authentication, and could interrupt operations if exposed. Prioritize discovery, network restriction, and vendor-guided remediation for reachable devices.
Technical view
CVE-2021-20999 is a CWE-668 exposure issue in Weidmüller u-controls and IoT-Gateways up to version 1.12.1. The port is reachable through external interfaces. The CVSS 3.1 score is 9.4, with network attack vector, low complexity, no privileges, no user interaction, and high integrity and availability impact.
Likely exposure
Exposure is most likely where affected UC20-WL2000-AC, UC20-WL2000-IOT, IOT-GW30, or IOT-GW30-4G-EU devices are reachable from corporate, partner, remote-access, or internet-adjacent networks. The source bundle lists versions 1.3.0, 1.10.0, and 1.11.0, and states versions up to 1.12.1 are affected.
Exploitation context
The provided sources do not state active exploitation, and the CVE is not marked KEV in the bundle. The risk is still high because exploitation is network-based, unauthenticated, low complexity, and could affect device operation in industrial or IoT environments.
Researcher notes
The bundle identifies the weakness as CWE-668 and provides CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H. Evidence is sufficient for exposure and severity, but the bundle does not include exploit details, observed exploitation, or a specific fixed version statement beyond affected versions up to 1.12.1.
Mitigation direction
- Identify affected Weidmüller devices and firmware versions in OT and remote-access networks.
- Restrict network access to device services from untrusted or unnecessary segments.
- Check Weidmüller and VDE guidance for fixed firmware or vendor-approved remediation.
- Prioritize remediation for devices reachable across routed networks or remote access paths.
- Monitor affected devices for unexpected configuration changes, faults, or stoppages.
Validation and detection
- Confirm device model and firmware version against the affected product list.
- Review firewall and segmentation rules for access to affected devices.
- Verify whether any external interface exposes services not required for operations.
- Check vendor advisories for current remediation status before changing production devices.
- Document compensating controls where immediate firmware remediation is not possible.
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-668: 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-2021-20999 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
- 9.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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:L/I:H/A:H3.95.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.4CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://cert.vde.com/en-us/advisories/vde-2021-016CVE reference · x_refsource_CONFIRM
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.
Exposure of Resource to Wrong Sphere
Exposure of Resource to Wrong Sphere represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.