CVE-2025-52376

Critical

Published: 15 July 2025

Published

15 July 2025

Modified

15 April 2026

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0021 43.1th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2025-52376 is a critical-severity Improper Authentication (CWE-287) vulnerability. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 43.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 AC-14 (Permitted Actions Without Identification or Authentication) and CM-7 (Least Functionality).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

AC-14 Permitted Actions Without Identification or Authentication good match

prevent

Directly identifies and restricts actions like enabling Telnet via the /web/um_open_telnet.cgi endpoint that can be performed without identification or authentication, preventing the bypass vulnerability.

IA-5 Authenticator Management good match

prevent

Prohibits the use of hard-coded credentials exposed by the Telnet service, blocking administrative shell access even if the service is enabled.

CM-7 Least Functionality good match

prevent

Prohibits or restricts unnecessary and insecure protocols like Telnet, eliminating the attack surface regardless of the authentication bypass.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1059.004 Unix Shell Execution

Adversaries may abuse Unix shell commands and scripts for execution.

attack.mitre.org →

Why these techniques?

Direct unauthenticated exploitation of public web endpoint (T1190) to enable Telnet daemon, followed by hard-coded credential login for Unix shell command execution (T1059.004).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

An authentication bypass vulnerability in the /web/um_open_telnet.cgi endpoint in Nexxt Solutions NCM-X1800 Mesh Router firmware UV1.2.7 and below, allowing an attacker to remotely enable the Telnet service without authentication, bypassing security controls. The Telnet server is then accessible with hard-coded…

credentials, allowing attackers to gain administrative shell access and execute arbitrary commands on the device.

Deeper analysisAI

CVE-2025-52376 is an authentication bypass vulnerability affecting the /web/um_open_telnet.cgi endpoint in Nexxt Solutions NCM-X1800 Mesh Router firmware versions UV1.2.7 and below. The flaw allows remote attackers to enable the Telnet service without any authentication, circumventing built-in security controls. Once enabled, the Telnet server exposes hard-coded credentials that grant administrative shell access. The vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) and is associated with CWE-287 (Improper Authentication) and CWE-798 (Use of Hard-coded Credentials).

Any unauthenticated remote attacker with network access to the vulnerable router can exploit this issue by sending a crafted request to the /web/um_open_telnet.cgi endpoint. This triggers the Telnet service to start, after which the attacker can connect using the hard-coded credentials to obtain full administrative privileges. Successful exploitation enables arbitrary command execution on the device, potentially leading to complete compromise, including data theft, configuration manipulation, or use as a pivot point in the network.

Public proof-of-concept exploits for CVE-2025-52376 are available on GitHub, including a detailed writeup documenting the attack methodology. No official vendor advisories or patches are referenced in available sources.