CVE-2021-21749Public exploitNetwork attack vector

Code execution via unchecked STK_PROCESS parameter copy

Published Oct 20, 2021 · Updated Aug 3, 2024

Stack-based buffer overflow in ZTE MF971R affected firmware allows remote attackers to execute arbitrary code via a crafted HTTP request. The STK_PROCESS handler copies the attacker-controlled stk_content parameter into a roughly 524-byte stack buffer with memcpy without checking its length. Remote exploitation requires a logged-in victim to visit an attacker-supplied URL and combines cross-site scripting, request-token calculation, and a Referer bypass; authenticated web-panel access reaches the flaw directly.

CVSS severity8.3
High
EPSS probability1.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in ZTE MF971R affected firmware allows remote attackers to execute arbitrary code via a crafted HTTP request. The STK_PROCESS handler copies the attacker-controlled stk_content parameter into a roughly 524-byte stack buffer with memcpy without checking its length. Remote exploitation requires a logged-in victim to visit an attacker-supplied URL and combines cross-site scripting, request-token calculation, and a Referer bypass; authenticated web-panel access reaches the flaw directly.

The record

CVE
CVE-2021-21749
Published
Oct 20, 2021
Updated
Aug 3, 2024
Vendor
ZTE Corporation
Product
ZTE MF971R
Classifications
CWE-121, CWE-787, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 20, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=BD_ZTE_MF971RV1.0.0B05, BD_PLKPLMF971R1V1.0.0B06, BD_MF971R2V1.0.0B03, BD_ZTE_MF971RS2V1.0.0B03, BD_ZTE_MF971RSV1.0.0B05

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ZTE Corporation · ZTE MF971Rversion=BD_ZTE_MF971RV1.0.0B05, BD_PLKPLMF971R1V1.0.0B06, BD_MF971R2V1.0.0B03, BD_ZTE_MF971RS2V1.0.0B03, BD_ZTE_MF971RSV1.0.0B05

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
8.3ZTE CorporationCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-121Stack-based Buffer Overflow
CWE-787Out-of-bounds Write
T1190Exploit Public-Facing Application

Public exploit references

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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