CVE-2021-37273: A Denial of Service issue exists in China Telecom Corporation EPON Tianyi Gateway ZXHN F450(EPON ONU) 3.0

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HIGH 7.5REMOTEMITIGATE

CVE-2021-37273 is a high-severity flaw (CVSS 7.5) affecting epon tianyi gateway zxhn f450 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A Denial of Service issue exists in China Telecom Corporation EPON Tianyi Gateway ZXHN F450(EPON ONU) 3.0. Tianyi Gateway is a hardware terminal of "Optical Modem Smart Router." Attackers can use this vulnerability to restart the device multiple times.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Published	2021-09-28
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: chinatelecom

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

Am I affected?

Timeline

2021-09-28 18:15 UTCPublished CVE record published
2026-06-17 04:00 UTCUpdated Record last modified

chinatelecom epon tianyi gateway zxhn f450 firmware MITIGATE

Affected: 3.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0

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-2021-37273?

epon tianyi gateway zxhn f450 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-37273 being exploited?

CVE-2021-37273 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-2021-37273 affect?

CVE-2021-37273 affects epon tianyi gateway zxhn f450 firmware. Severity is high (CVSS 7.5). A Denial of Service issue exists in China Telecom Corporation EPON Tianyi Gateway ZXHN F450(EPON ONU) 3.0. Tianyi Gateway is a hardware terminal of "Optical Modem Smart Router." Attackers can use this vulnerability to restart the device mul

How urgent is CVE-2021-37273?

Priority 47/100. High severity; Remotely exploitable, no login, no user action

References

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