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CVE Record

CVE-2021-3297: On Zyxel NBG2105 V1.00(AAGU.2)C0 devices, setting the login cookie to 1 provides administrator access.

On Zyxel NBG2105 V1.00(AAGU.2)C0 devices, setting the login cookie to 1 provides administrator access.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-3297 is an administrator authentication bypass affecting Zyxel NBG2105 V1.00(AAGU.2)C0 devices. The public CVE description says administrator access can be obtained by manipulating the login cookie. For executives, treat any matching router as a potentially high-impact edge-device risk, especially if its management interface is reachable from untrusted networks.

Executive priority

Prioritize promptly if this model exists in production or remote administration is enabled. It is not listed as actively exploited in the supplied data, but administrator bypass on a router can lead to network compromise.

Technical view

The vulnerability is described as a web administration session/authentication flaw: a specific login cookie value grants administrator access on Zyxel NBG2105 V1.00(AAGU.2)C0. The bundle provides no CVSS score, CWE, confirmed fixed version, or vendor mitigation text. Public researcher references exist, but active exploitation is not indicated by KEV or the supplied sources.

Likely exposure

Exposure appears limited to Zyxel NBG2105 devices running V1.00(AAGU.2)C0. Risk is highest where the web management interface is reachable from the internet, guest networks, or broad internal networks.

Exploitation context

The supplied sources support public disclosure and researcher writeups, but not confirmed active exploitation. CISA KEV status is false in the bundle. The weakness is still serious because it concerns administrator access to a network edge device.

Researcher notes

Evidence is sparse and version-specific. The bundle lacks CVSS, CWE, patch details, and vendor remediation text. Research should focus on confirming device presence, firmware state, management-plane exposure, and whether Zyxel has updated guidance for NBG2105.

Mitigation direction

  • Inventory Zyxel NBG2105 devices and record firmware versions.
  • Check Zyxel security and support pages for official firmware or retirement guidance.
  • Disable internet-facing or untrusted access to the management interface.
  • Restrict administration to trusted management networks or VPN access.
  • Replace or isolate affected devices if no vendor-supported fix is available.

Validation and detection

  • Confirm whether any NBG2105 runs V1.00(AAGU.2)C0.
  • Verify the management interface is not exposed to the internet.
  • Review device configuration for remote administration settings.
  • Check administrative logs for unexpected configuration changes.
  • Validate remediation using only authorized, non-destructive testing.
Prepared
Confidence
medium
Sources
6

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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CVE-2021-3297 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
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

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.