CVE-2021-21724

Service interruption via optical-signal memory leak

Published Feb 26, 2021 · Updated Aug 3, 2024

Memory leak in ZTE ZXR10 8900E firmware through 3.03.20R2B30P1 allows local users with device permissions to interrupt service. The optical-signal handling path fails to release memory when the signal is repeatedly attenuated, progressively exhausting device memory. Exploitation requires device permissions and repeated optical attenuation; the published consequence is abnormal service, not a persistent device failure.

CVSS severity4.4
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in ZTE ZXR10 8900E firmware through 3.03.20R2B30P1 allows local users with device permissions to interrupt service. The optical-signal handling path fails to release memory when the signal is repeatedly attenuated, progressively exhausting device memory. Exploitation requires device permissions and repeated optical attenuation; the published consequence is abnormal service, not a persistent device failure.

The record

CVE
CVE-2021-21724
Published
Feb 26, 2021
Updated
Aug 3, 2024
Vendor
ZTE Corporation
Product
ZXR10 8900E
Classifications
CWE-401, T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Feb 26, 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 V3.03.20R2B30P1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

ZTE Corporation · ZXR10 8900Eversion=all versions up to V3.03.20R2B30P1

Published CVSS scores

4.4NIST NVDCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:P

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)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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