CVE-2021-37386: Furukawa Electric LatAm 423-41W/AC before v1.1.4 and LD421-21W before v1.3.3 were discovered to contain an HTM

Q: How do I fix CVE-2021-37386?

423-41w\/ac firmware: upgrade to 1.2.0; ld421-21w firmware: upgrade to 1.5.0; ld420-10r firmware: upgrade to 1.4.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-37386 being exploited?

CVE-2021-37386 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-37386 affect?

CVE-2021-37386 affects 423-41w\/ac firmware, ld421-21w firmware, ld420-10r firmware. Severity is high (CVSS 7.5). Furukawa Electric LatAm 423-41W/AC before v1.1.4 and LD421-21W before v1.3.3 were discovered to contain an HTML injection vulnerability via the serial number update function.

Routine

HIGH 7.5UPGRADEUPGRADEUPGRADE

CVE-2021-37386 is a high-severity flaw (CVSS 7.5) affecting 423-41w\/ac firmware, ld421-21w firmware, ld420-10r firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Furukawa Electric LatAm 423-41W/AC before v1.1.4 and LD421-21W before v1.3.3 were discovered to contain an HTML injection vulnerability via the serial number update function.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	Required
EPSS exploit chance	0.5% (top 54%)
CISA exploited list	No
Weakness	CWE-79
Published	2023-07-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: furukawa

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2023-07-17 17:15 UTCPublished CVE record published
2026-06-17 04:00 UTCUpdated Record last modified

furukawa 423-41w\/ac firmware UPGRADE

Affected: < 1.2.0

Fixed in: 1.2.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

furukawa ld421-21w firmware UPGRADE

Affected: < 1.5.0

Fixed in: 1.5.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

furukawa ld420-10r firmware UPGRADE

Affected: < 1.4.0

Fixed in: 1.4.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

furukawa ld421-21wv firmware UPGRADE

Affected: < 1.5.0

Fixed in: 1.5.0

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-37386?

423-41w\/ac firmware: upgrade to 1.2.0; ld421-21w firmware: upgrade to 1.5.0; ld420-10r firmware: upgrade to 1.4.0. Exact commands for each OS are on this page.

Is CVE-2021-37386 being exploited?

CVE-2021-37386 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-37386 affect?

CVE-2021-37386 affects 423-41w\/ac firmware, ld421-21w firmware, ld420-10r firmware. Severity is high (CVSS 7.5). Furukawa Electric LatAm 423-41W/AC before v1.1.4 and LD421-21W before v1.3.3 were discovered to contain an HTML injection vulnerability via the serial number update function.

How urgent is CVE-2021-37386?

Priority 38/100. High severity

Related CVEs

CVE-2021-37384 CRITICAL 9.8 UPGRADE UPGRADE RCE (Remote Code Execution) vulnerability was found in some Furukawa ONU models, this vulnerability allows rem

References

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