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Vulnerabilities

Vulnerability · CVE-2021-3297

Zyxel nbg2105_firmware Improper Authentication

Published Aug 19, 2025 · catalog updated Aug 19, 2025 · Zyxel

Patch now

CVE-2021-3297 is in the CISA known-exploited catalog. Confirm Zyxel against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
Severity
Unknown—
Known exploitation
CISA KEV and VulnCheck KEV
EPSS
20.51%
Remediation
Remediation guidance
Affected products
vendor Zyxel nbg2105_firmware

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Zyxel nbg2105_firmwareversion unspecified

How to fix CVE-2021-3297

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2021-3297 is in the CISA known-exploited catalog. Confirm Zyxel against the vendor advisory and apply that fix. The CVSS score does not change the priority.

Which versions are affected?

Affected version ranges are not on this record. Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

What should an analyst verify?

No weakness class is stored. EPSS 20.51%. The CISA KEV listing is the exploitation evidence. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 19, 2025 · VulnCheck KEV

    Detected

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

  2. Aug 19, 2025 · CISA KEV

    Known exploited

    Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.

Sources

  • CVE.orgVulnerability recordCVE-2021-3297

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-3297

    30-day exploitation probability 20.5%

    first.org
  • VulnCheck KEVConfirmed exploitationCVE-2021-3297

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

    vulncheck.com

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.