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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Authentication mechanism validation
MITRE ATT&CK

2 techniques across 2 tactics: Defense Evasion, Initial Access

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 9.1 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.

Exploit ScenarioDerived

A remote attacker could bypass authentication mechanisms to gain unauthorized access by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.
No patch listed yet 1.3% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Implement multi-factor authentication, enforce strong password policies, use proven authentication frameworks.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Improper Authentication (CWE-287), which allows attackers to bypass authentication mechanisms to gain unauthorized access. An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Through an undocumented sequence of keypresses, undocumented functionality is triggered. A diagnostics shell is triggered via CTRL-ALT-t, which prompts for the password returned by fds_sys_passDebugPasswd_ret(). The firmware contains access control checks that determine if remote users are allowed to access this functionality. The function that performs this check (fds_sys_remoteDebugEnable_ret in libfds.so) always return TRUE with no actual checks performed. The diagnostics menu allows for reading/writing arbitrary registers and various other configuration parameters which are believed to be related to the network interface chips. Affected products include: Zyxel Gs1900-8 Firmware, Zyxel Gs1900-8Hp Firmware, Zyxel Gs1900-10Hp Firmware, Zyxel Gs1900-16 Firmware, Zyxel Gs1900-24E Firmware. Version information: before 2.50.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.1 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

DescriptionNVD

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Through an undocumented sequence of keypresses, undocumented functionality is triggered. A diagnostics shell is triggered via CTRL-ALT-t, which prompts for the password returned by fds_sys_passDebugPasswd_ret(). The firmware contains access control checks that determine if remote users are allowed to access this functionality. The function that performs this check (fds_sys_remoteDebugEnable_ret in libfds.so) always return TRUE with no actual checks performed. The diagnostics menu allows for reading/writing arbitrary registers and various other configuration parameters which are believed to be related to the network interface chips.

Threat Intelligence Overview

EPSS Score
1.3%
Top 32% exploitable
Exploit
POC
Public exploit code exists
Data Quality
2 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC Yes
EPSS 1.3%
Patch available No
Active threat No
Deciding rule
CRITICAL severity + public POC available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

67
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +46
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:o:zyxel:gs1900-8_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-8hp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-10hp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-16_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-24e_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-24_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-24hp_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-48_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:zyxel:gs1900-48hp_firmware:*:*:*:*:*:*:*:*
CVE-2026-7273 HIGH POC
8.8 Jun 16

Remote code execution in Zyxel GS1900 series managed switches (including GS1900-48HPv2, GS1900-8, GS1900-8HP, GS1900-10H

CVE-2019-15800 CRITICAL POC
9.8 Nov 14

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated critical severity (CVSS 9.8),

CVE-2019-15799 HIGH POC
8.8 Nov 14

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated high severity (CVSS 8.8), thi

CVE-2019-15804 HIGH POC
7.5 Nov 14

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated high severity (CVSS 7.5), thi

CVE-2019-15801 HIGH POC
7.5 Nov 14

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated high severity (CVSS 7.5), thi

CVE-2015-5989 CRITICAL
9.8 Dec 31

Belkin F9K1102 2 devices with firmware 2.10.17 rely on client-side JavaScript code for authorization, which allows remot

CVE-2016-1329 CRITICAL
9.8 Mar 03

Cisco NX-OS 6.0(2)U6(1) through 6.0(2)U6(5) on Nexus 3000 devices and 6.0(2)A6(1) through 6.0(2)A6(5) and 6.0(2)A7(1) on

CVE-2015-5988 CRITICAL
9.8 Dec 31

The web management interface on Belkin F9K1102 2 devices with firmware 2.10.17 has a blank password, which allows remote

CVE-2019-15802 MEDIUM POC
5.9 Nov 14

An issue was discovered on Zyxel GS1900 devices with firmware before 2.50(AAHH.0)C0. Rated medium severity (CVSS 5.9), t

CVE-2016-1302 HIGH
8.8 Feb 07

Cisco Application Policy Infrastructure Controller (APIC) devices with software before 1.0(3h) and 1.1 before 1.1(1j) an

CVE-2015-5990 HIGH
8.8 Dec 31

Cross-site request forgery (CSRF) vulnerability on Belkin F9K1102 2 devices with firmware 2.10.17 allows remote attacker

CVE-2015-5987 HIGH
8.6 Dec 31

Belkin F9K1102 2 devices with firmware 2.10.17 use an improper algorithm for selecting the ID value in the header of a D

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