Security readout for executives and security teams
Plain-English summary
This flaw affects specific Furukawa Electric LatAm router/ONT models and lets a privileged user place HTML into the serial number update workflow. It can affect what another user sees in the web interface and may disrupt availability. Business urgency depends on whether these devices are deployed and reachable for administration.
Executive priority
Treat as a targeted operational risk for affected network edge devices. Prioritize inventory and management-plane restrictions first, then firmware updates through approved vendor processes. Do not assume exposure if these Furukawa models are not deployed.
Technical view
CVE-2021-37386 is an HTML injection issue, mapped to CWE-79, in the serial number update function of Furukawa Electric LatAm 423-41W/AC before v1.1.4 and LD421-21W before v1.3.3. CVSS 3.1 is 7.5 with network attack vector, high privileges required, user interaction required, changed scope, and high availability impact.
Likely exposure
Exposure appears limited to organizations running Furukawa Electric LatAm 423-41W/AC below v1.1.4 or LD421-21W below v1.3.3. The affected product fields in the bundle are incomplete, so confirm models and firmware directly from device inventory.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. The CVSS vector indicates exploitation requires network access, high privileges, and user interaction, which lowers mass-exploitation likelihood but still matters for exposed management interfaces.
Researcher notes
The bundle names HTML injection in a privileged serial number update function, but does not include full vendor advisory detail or proof of active exploitation. Analyze exposure around admin access paths, stored interface rendering, and firmware versions below the stated thresholds.
Mitigation direction
- Inventory Furukawa Electric LatAm 423-41W/AC and LD421-21W devices.
- Upgrade 423-41W/AC to v1.1.4 or later where vendor-supported.
- Upgrade LD421-21W to v1.3.3 or later where vendor-supported.
- Restrict management interfaces to trusted admin networks.
- Review vendor or maintainer guidance before applying firmware changes.
Validation and detection
- Confirm device model and firmware version from trusted inventory records.
- Check whether serial number update functionality is reachable by nonessential administrators.
- Review web management logs for suspicious serial number changes.
- Verify management interfaces are not internet-exposed.
- After upgrade, confirm firmware reports the expected fixed version.
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-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. 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-2021-37386 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
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/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:H/UI:R/S:C/C:L/I:L/A:H1.75.3Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://cwe.mitre.org/data/definitions/79.htmlCVE reference
- https://owasp.org/www-project-web-security-testing-guide/latest/4-Web_Application_Security_Testing/11-Client-side_Testing/03-Testing_for_HTML_InjectionCVE reference
- https://gist.githubusercontent.com/LuigiPolidorio/ec78daac7c3d97966f2e3703ca5d1685/raw/d64a487407d6f9685d3907206954a6c84c6fa621/reference.txtCVE reference
- https://www.softwall.com.br/cves/publicacao-rce-html-injection-furukawa/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.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.