How severe is CVE-2021-34203?

CVE-2021-34203 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-34203 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34203?

CVE-2021-34203 affects Dlink Dir-2640-us Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-34203?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-34203 published?

CVE-2021-34203 was published on 2021-06-16 and last updated on 2026-07-05.

CVE-2021-34203

CVE-2021-34203 is a high-severity vulnerability in Dlink Dir-2640-us Firmware with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1188.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 4.8
EPSS exploit prediction: 2% (73rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1188
Affected product: Dlink Dir-2640-us Firmware
Published: 2021-06-16
Last modified: 2026-07-05

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.

Frequently asked questions

What is CVE-2021-34203?: 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 severe is CVE-2021-34203?: CVE-2021-34203 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-34203 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34203?: CVE-2021-34203 affects Dlink Dir-2640-us Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-34203?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-34203 published?: CVE-2021-34203 was published on 2021-06-16 and last updated on 2026-07-05.

References

Affected products (1)

cpe:2.3:o:dlink:dir-2640-us_firmware:1.01b04:*:*:*:*:*:*:*

More vulnerabilities in Dlink Dir-2640-us Firmware

CVE-2021-20132 — High (CVSS 8.8): Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 use default hard-coded credentials, which can…
CVE-2021-20134 — High (CVSS 8.4): Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 are affected by an absolute path traversal…
CVE-2021-34202 — High (CVSS 7.8): There are multiple out-of-bounds vulnerabilities in some processes of D-Link AC2600(DIR-2640) 1.01B04. Ordinary…
CVE-2021-34201 — High (CVSS 7.1): D-Link DIR-2640-US 1.01B04 is vulnerable to Buffer Overflow. There are multiple out-of-bounds vulnerabilities in some…
CVE-2021-34204 — Medium (CVSS 6.8): D-Link DIR-2640-US 1.01B04 is affected by Insufficiently Protected Credentials. D-Link AC2600(DIR-2640) stores the…
CVE-2021-20133 — Medium (CVSS 6.1): Quagga Services on D-Link DIR-2640 less than or equal to version 1.11B02 are affected by an absolute path traversal…

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