CVE-2021-34203Public exploit

Routing takeover via exposed default Quagga credentials

Published Jun 16, 2021 · Updated Jul 9, 2026

Incorrect access control in D-Link DIR-2640-US 1.01B04 allows remote attackers to access Quagga routing services over Telnet. Enabling PPPoE starts the Quagga zebra and ripd services on the network, where they accept the original default password on their standard Telnet ports. Network access to the router is sufficient to alter routing and DNS data or inspect traffic handled by the device.

CVSS severity8.1
High
EPSS probability1.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect access control in D-Link DIR-2640-US 1.01B04 allows remote attackers to access Quagga routing services over Telnet. Enabling PPPoE starts the Quagga zebra and ripd services on the network, where they accept the original default password on their standard Telnet ports. Network access to the router is sufficient to alter routing and DNS data or inspect traffic handled by the device.

The record

CVE
CVE-2021-34203
Published
Jun 16, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1188, T1078.001
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
4.8NIST NVDAV:A/AC:L/Au:N/C:P/I:P/A:N

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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1188Insecure Default Initialization of Resource
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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