CVE-2021-21819Public exploitNetwork attack vector

Authenticated command execution via unsanitized Libcli arguments

Published Jul 16, 2021 · Updated Aug 3, 2024

OS command injection in the Libcli Test Environment of D-Link DIR-3040 1.13B03 allows remote authenticated users to execute commands. The ping and ated handlers pass arguments containing command separators to systemCmd without sanitization. Exploitation requires the hidden Telnet service and administrator credentials, and injected commands run with the router's privileges.

CVSS severity7.2
High
EPSS probability2.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in the Libcli Test Environment of D-Link DIR-3040 1.13B03 allows remote authenticated users to execute commands. The ping and ated handlers pass arguments containing command separators to systemCmd without sanitization. Exploitation requires the hidden Telnet service and administrator credentials, and injected commands run with the router's privileges.

The record

CVE
CVE-2021-21819
Published
Jul 16, 2021
Updated
Aug 3, 2024
Vendor
D-Link
Product
DIR-3040
Classifications
CWE-78, T1059.008
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jul 16, 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=D-LINK DIR-3040 1.13B03

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

D-Link · DIR-3040version=D-LINK DIR-3040 1.13B03

Published CVSS scores

9.1Cisco TalosCVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
9.0NIST NVDAV:N/AC:L/Au:S/C:C/I:C/A:C

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-78Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
T1059.008Command and Scripting Interpreter: Network Device CLI

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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