CVE-2021-21728

Processing-capacity degradation via default-open port flooding

Published Apr 9, 2021 · Updated Aug 3, 2024

Resource exhaustion in ZTE ZXA10 C300M 4.3P8 and earlier allows attackers to reduce processing capacity via packet flooding. The default-open network port processes a high packet volume without limiting consumption of system processing resources. No authentication or user interaction is required; sustained traffic degrades capacity, but the vendor does not report a crash or reboot.

CVSS severity3.1
Low
EPSS probability0.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in ZTE ZXA10 C300M 4.3P8 and earlier allows attackers to reduce processing capacity via packet flooding. The default-open network port processes a high packet volume without limiting consumption of system processing resources. No authentication or user interaction is required; sustained traffic degrades capacity, but the vendor does not report a crash or reboot.

The record

CVE
CVE-2021-21728
Published
Apr 9, 2021
Updated
Aug 3, 2024
Vendor
ZTE Corporation
Product
ZXA10 C300M
Classifications
CWE-400, T1499.002
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=all versions up to V4.3P8

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

ZTE Corporation · ZXA10 C300Mversion=all versions up to V4.3P8

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
3.1ZTE CorporationCVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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