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CVE Record

CVE-2021-34203: D-Link DIR-2640-US 1.01B04 is vulnerable to Incorrect Access Control.

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-34203 concerns a reported access-control flaw in D-Link DIR-2640-US firmware 1.01B04. When PPPoE is configured, a routing-related service may be exposed using default access, potentially allowing traffic monitoring, route changes, DNS hijacking, and phishing risk for devices behind the router.

Executive priority

Prioritize review where this router protects business users or remote offices. The reported impact reaches traffic visibility and DNS manipulation, but urgency depends on confirmed device presence, PPPoE use, and vendor remediation status.

Technical view

The report says PPPoE configuration starts a Quagga process in broad network-monitoring mode and leaves its original default password and port accessible. The CVE record provides no CVSS score, CWE, complete CPE data, or confirmed fixed version in the supplied sources.

Likely exposure

Exposure appears limited to D-Link DIR-2640-US firmware 1.01B04 where PPPoE is configured. Asset inventories should confirm model, firmware, WAN configuration, and whether any unexpected routing-management service is reachable.

Exploitation context

The CVE is not listed as KEV in the supplied bundle, and no cited source states active exploitation. The public report describes straightforward misuse if the exposed service is reachable, but evidence is incomplete.

Researcher notes

The supplied CVE metadata is sparse: affected fields are n/a, severity is unknown, and no patch version is named. Treat the GitHub report and CVE description as primary leads, then corroborate against D-Link guidance before asserting remediation completeness.

Mitigation direction

  • Check D-Link security bulletins for model-specific firmware guidance.
  • Upgrade firmware only according to verified D-Link guidance.
  • Avoid PPPoE configuration on affected firmware where operationally possible.
  • Restrict router administrative and service exposure to trusted management networks.
  • Replace affected devices if no vendor-supported remediation exists.

Validation and detection

  • Identify any DIR-2640-US devices and record firmware versions.
  • Confirm whether PPPoE is configured on each device.
  • Review router services for unexpected externally reachable routing management interfaces.
  • Check logs and configuration for unauthorized routing or DNS changes.
  • Monitor downstream clients for DNS redirection or phishing indicators.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-34203 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
3Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.