CVE-2021-21913Public exploitNetwork attack vector

Root-password disclosure via hard-coded MQTT credentials

Published Sep 23, 2021 · Updated Aug 3, 2024

Information disclosure in D-Link DIR-3040 1.13B03 allows remote attackers to obtain the primary router's root password via MQTT. The default-enabled MQTT service uses credentials embedded in libapson_mqtt_api.so, while apson encrypts mesh payloads with a key derived from the publisher's exposed MAC address. Network access to MQTT permits decryption of the propagated password, enabling administrator access or payloads that reboot or evict mesh devices.

CVSS severity10.0
Critical
EPSS probability2.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in D-Link DIR-3040 1.13B03 allows remote attackers to obtain the primary router's root password via MQTT. The default-enabled MQTT service uses credentials embedded in libapson_mqtt_api.so, while apson encrypts mesh payloads with a key derived from the publisher's exposed MAC address. Network access to MQTT permits decryption of the propagated password, enabling administrator access or payloads that reboot or evict mesh devices.

The record

CVE
CVE-2021-21913
Published
Sep 23, 2021
Updated
Aug 3, 2024
Vendor
D-Link
Product
DIR-3040
Classifications
CWE-798, T1078
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 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 privilegesunauthenticated

What is affected?

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

Published CVSS scores

10.0Cisco TalosCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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

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-798Use of Hard-coded Credentials
T1078Valid Accounts

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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