CVE-2021-34203
HIGHDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 65% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1188 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2020-13927 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2023-27524 | High | 8.9 | 97% | KEV | - |
| CVE-2022-24706 | Critical | 9.8 | 92% | KEV | Fix |
| CVE-2020-11532 | Critical | 9.8 | 77% | - | Fix |
| CVE-2018-16752 | High | 8.8 | 36% | - | - |
| CVE-2020-14011 | Critical | 9.8 | 29% | - | - |
Common questions
How do I fix CVE-2021-34203?
No published fix for CVE-2021-34203 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2021-34203 being actively exploited?
Not that we know of. CVE-2021-34203 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 1.2% is the estimated probability that it will be exploited in the next 30 days. That is higher than 65% of all scored CVEs.
How severe is CVE-2021-34203?
CVE-2021-34203 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-09.