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Vulnerability record · CVE-2021-34203 · published 16 June 2021

CVE-2021-34203: Dlink dir-2640-us firmware insecure default initialization vulnerability

Dlink · Dir 2640 Us Firmware

D-Link DIR-2640-US 1.01B04 is vulnerable to Incorrect Access Control. Router ac2600 (dir-2640-us), when setting PPPoE, will start quagga process in the way of whole network monitoring, and this function uses the original default password and port. An attacker can easily use telnet to log in, modify routing information, monitor the traffic of all devices under the router, hijack DNS and phishing attacks. In addition, this interface is likely to be questioned by customers as a backdoor, because the interface should not be exposed.

8.1 CVSS 3.1 High EPSS 1.2% · top 33.2% CWE-1188 · Insecure default initialization
8.1CVSS 3.1 base score, v2 4.8
1.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
9 Jul 2026Last modified by NVD

Description

D-Link DIR-2640-US 1.01B04 is vulnerable to Incorrect Access Control. Router ac2600 (dir-2640-us), when setting PPPoE, will start quagga process in the way of whole network monitoring, and this function uses the original default password and port. An attacker can easily use telnet to log in, modify routing information, monitor the traffic of all devices under the router, hijack DNS and phishing attacks. In addition, this interface is likely to be questioned by customers as a backdoor, because the interface should not be exposed.

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/liyansong2018/CVE/tree/main/2021/CVE-2021-34203 ExploitThird Party Advisory
https://www.dlink.com/en/security-bulletin/ Vendor Advisory
https://github.com/liyansong2018/CVE/tree/main/2021/CVE-2021-34203 ExploitThird Party Advisory
https://www.dlink.com/en/security-bulletin/ Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-34203), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.