CVE-2021-39613Public exploit

Root access via crackable hard-coded Telnet credentials

Published Aug 23, 2021 · Updated Aug 4, 2024

Hard-coded credentials in D-Link DVG-3104MS firmware 1.0.2.0.3, 1.0.2.0.4, and 1.0.2.0.4E allow remote attackers to gain root access. The firmware stores undocumented account hashes in /etc/passwd using weak passwords, enabling dictionary recovery of credentials accepted by Telnet. Network access to Telnet is required; successful login grants an embedded Linux shell, including through accounts assigned user ID zero.

CVSS severity8.8
High
EPSS probability1.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Hard-coded credentials in D-Link DVG-3104MS firmware 1.0.2.0.3, 1.0.2.0.4, and 1.0.2.0.4E allow remote attackers to gain root access. The firmware stores undocumented account hashes in /etc/passwd using weak passwords, enabling dictionary recovery of credentials accepted by Telnet. Network access to Telnet is required; successful login grants an embedded Linux shell, including through accounts assigned user ID zero.

The record

CVE
CVE-2021-39613
Published
Aug 23, 2021
Updated
Aug 4, 2024
Vendor
D-Link
Product
DVG-3104MS Firmware
Classifications
CWE-798, T1078.001
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=1.0.2.0.3
  2. Affected versionversion=1.0.2.0.4
  3. Affected versionversion=1.0.2.0.4e

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

D-Link · DVG-3104MS Firmwareversion=1.0.2.0.3; version=1.0.2.0.4; version=1.0.2.0.4e

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
8.8CISA ADPCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/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

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-798Use of Hard-coded Credentials
T1078.001Default 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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