CVE-2021-21748Public exploitNetwork attack vector

Remote code execution via unchecked password length

Published Oct 20, 2021 · Updated Aug 3, 2024

Stack-based buffer overflow in ZTE MF971R firmware allows remote attackers to execute code through a crafted HTTP request. The ADB_MODE_SWITCH handler passes an unchecked password value to my_string_to_hex, which decodes it into a fixed 1,040-byte stack buffer. Exploitation requires a victim to visit an attacker-controlled URL, but no router login is required; success grants code execution on the device.

CVSS severity9.6
Critical
EPSS probability1.78%
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 firmware allows remote attackers to execute code through a crafted HTTP request. The ADB_MODE_SWITCH handler passes an unchecked password value to my_string_to_hex, which decodes it into a fixed 1,040-byte stack buffer. Exploitation requires a victim to visit an attacker-controlled URL, but no router login is required; success grants code execution on the device.

The record

CVE
CVE-2021-21748
Published
Oct 20, 2021
Updated
Aug 3, 2024
Vendor
ZTE Corporation
Product
MF971R
Classifications
CWE-787, CWE-121, T1203
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 · 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
9.6ZTE CorporationCVSS:3.1/AV:N/AC:L/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.

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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-787Out-of-bounds Write
CWE-121Stack-based Buffer Overflow
T1203Exploitation for Client Execution

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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