CVE-2021-3297 (GCVE-0-2021-3297)

Vulnerability from cvelistv5 – Published: 2021-01-26 07:11 – Updated: 2025-11-25 17:27
VLAI Shadowserver Previdian
Summary
On Zyxel NBG2105 V1.00(AAGU.2)C0 devices, setting the login cookie to 1 provides administrator access.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
  • n/a
Assigner
References
Shadowserver
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 476000c5-fae9-4bcc-ae74-eb9c95f9d79e

Vulnerability ID: CVE-2021-3297

Status: Confirmed

Status Updated: 2026-09-06 00:00 UTC

Exploited: Yes

Characteristics
Severity: 78.0
Timestamps
First Seen: 2025-08-19
Asserted: 2025-08-19
Last Seen: 2026-09-06
Scope
Asset Exposure: ['internet-facing']
Notes: Affected: Zyxel / Zyxel NBG2105 | Class: router | Severity: High (CVSS 7.8) | IoT: yes | In CISA KEV: no | Honeypot connections on 2026-09-06: 30
Evidence

Type: Honeypot

Signal: In The Wild Attempts

Confidence: 70%

Source: shadowserver

Details
1D 3
Iot yes
Feed Shadowserver Foundation honeypot/exploited-vulnerabilities
Type http-scan
Class router
7D Avg 2
Vendor Zyxel
30D Avg 1
90D Avg 1
Product Zyxel NBG2105
Cisa Kev no
Connections 30
Observation Date 2026-09-06
Vulnerability Class CVSS
Vulnerability Score 7.8
Vulnerability Severity High
References
Created: 2026-07-01 05:54 UTC | Updated: 2026-09-08 01:01 UTC
Previdian
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: f07c3869-6232-44a9-9d0a-cf9962c24f9c

Vulnerability ID: CVE-2021-3297

Status: Confirmed

Status Updated: 2025-09-16 00:00 UTC

Exploited: Yes

Timestamps
First Seen: 2025-09-16
Asserted: 2025-09-16
Scope
Notes: KEVIntel entry: On Zyxel NBG2105 V1.00(AAGU.2)C0 devices, setting the login cookie to 1 provides administrator access. | Affected: Zyxel / NBG2105 | CVSS: 7.8 (HIGH) | Used in malware: unknown | Not yet in CISA KEV: True
Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: kevintel

Details
Feed KEVIntel (kevintel.com)
Title On Zyxel NBG2105 V1.00(AAGU.2)C0 devices, setting the login cookie to 1 provides administrator access.
Vendor Zyxel
Product NBG2105
Added Date 2025-09-16T00:00:00.000Z
Cvss Score 7.8
Epss Score None
Cvss Severity HIGH
Epss Percentile None
Used In Malware unknown
Ahead Of Cisa Kev None
Not Yet In Cisa Kev True
References
Created: 2026-06-19 12:42 UTC | Updated: 2026-06-19 12:42 UTC
Show details on NVD website
To clipboard 

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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.