Security readout for executives and security teams
Plain-English summary
CVE-2021-31399 affects 2N Access Unit 2.0 2.31.0.40.5 devices. A nearby network attacker may be able to impersonate the web relay and place themselves between communications. Business risk is moderate because this concerns physical access-control infrastructure, but the published score is medium and requires adjacent access plus user interaction.
Executive priority
Treat this as a targeted infrastructure hygiene issue, not an emergency internet-wide incident. Prioritize sites where access-control devices share networks with untrusted users or contractors.
Technical view
The CVE describes a man-in-the-middle condition where an unauthenticated adjacent attacker can pose as the web relay. CVSS 3.1 is 4.6 with low attack complexity, adjacent-network access, no privileges, required user interaction, low confidentiality impact, no integrity impact, and low availability impact.
Likely exposure
Exposure is most likely in organizations running 2N Access Unit 2.0 firmware 2.31.0.40.5 on reachable local or facility networks. The source bundle does not identify broader affected versions or products.
Exploitation context
The source bundle does not report active exploitation, and CISA KEV status is false. Exploitation appears constrained to adjacent-network positioning and requires user interaction, limiting broad internet-scale risk but still relevant for building access systems.
Researcher notes
Public metadata is sparse: no CWE is listed, affected CPEs are unavailable, and the bundle does not name a patch. Avoid expanding scope beyond 2N Access Unit 2.0 2.31.0.40.5 without vendor confirmation.
Mitigation direction
- Check 2N and advisory guidance for corrected firmware or official workarounds.
- Inventory 2N Access Unit 2.0 devices and identify firmware 2.31.0.40.5.
- Restrict management and relay access to trusted administrative networks.
- Segment physical access-control devices from general user networks.
- Monitor vendor advisories for updated affected-version and remediation details.
Validation and detection
- Confirm whether any 2N Access Unit 2.0 devices run firmware 2.31.0.40.5.
- Review network reachability from user, guest, and facility network segments.
- Check logs for unusual web relay connections or unexpected device communication paths.
- Verify whether vendor guidance has been applied to affected devices.
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-2021-31399 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
- Medium
- CVSS
- 4.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AC:L/AV:A/A:L/C:L/I:N/PR:N/S:U/UI:R
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/AC:L/AV:A/A:L/C:L/I:N/PR:N/S:U/UI:R2.12.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.6MediumVector: CVSS:3.1/AC:L/AV:A/A:L/C:L/I:N/PR:N/S:U/UI:R
Source materials
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.